I think the math for deciding this can get pretty complex, and potentially very personal as well. It comes down to what you value. Let's take my own flying as an example. My patterns mean that at the moment by sticking to AFKL, I can get to Ulti relatively easily. I could move my frequent flyer program to someone else in SkyTeam, let's say Delta, and would probably end up at Diamond with all the flying from AFKL being credited there because MQD would be converted from the distance rather than the actual dollar value.

Given my location, if I were to stay within SkyTeam, 90% of my flying would be on AFKL due to network reasons, with some VS mixed in, and occasional trips on VN, MU, MF, CI and KE. Considering this, if I were STE+ through Delta as a Diamond, what benefits would I actually receive on 90% of my travel? Comparing this to being a Plat with FB, here’s what I see:

• The GUCs would get me upgrades on many airlines. Delta gets this win.
• I would get access to the same lounges, mostly, as AFKL gets to me. So we're equal there.
• My redemption opportunities would be pretty terrible. In theory, Delta should have access to similar partners, but FB has other non-SkyTeam earn/burn and more redemptions available at reasonable rates. At least for me. I value this a lot because I can currently redeem around 5-6 long-haul J trips in a year with my earnings. FB wins here.
• I get one extra bag as STE+ on all ST airlines. So equal there.
• But as Plat I get 2 extra bags on AFKL, where 90% of my flying is, so FB gets a small win here.
• I will still be stuck on AFKL metal for most of my flights, so my free seat selection from the moment of booking goes away. My cost structure increases. FB wins.
• For other ST airlines, with seat selection, I am treated as whatever STE+ gets. So that's equal.
• Boarding at ST airlines, I get priority with both as STE+. So we're equal there.
• When it comes to IRROPs, most ST airlines will give me some level of priority as STE+ on re-booking, but it will be after their own elites. For ST airlines in general, this is equal.
• For IRROPs with AFKL, where 90% of my travel is centered, as Plat I get generally really good IRROPs handling by the PSL. I've even had them fix interline ticket issues, while I was at the check-in desk within minutes of calling. I almost always got where I needed to be, with priority over most other passengers. Btw, I know the PSL continues to be mostly great with these things (except some occasional reports of issues) because the rest of my family is Plat and keeps getting the same great service. Win for FB.

Looking at all of that, given my location and what airlines I'd end up picking in ST, the score comes out as:

• Delta wins 1.
• Equal on 5.
• FB wins on 4.

So FB comes out clearly the winner for my situation, especially because most of my flying would be AFKL and not other ST airlines. Also, even as Plat, I've personally always valued being able to get issues with my flights resolved more than anything else. Since the PSL made that always possible without pains, for me personally I'd put weightage on each point and that would would be weighted very heavily, leading to a clear win. That's what I meant by personal math. Perhaps if I had a large spread across ST, then I would benefit from a different program (maybe even Delta's).

If you ultra optimize your flying patterns, you could get Plat for as little spend as €3000-€4000. This is still a good bit cheaper than what Diamond at Delta would cost. Plus, hold on to this for 10 years, and you get to keep it for life too. On just personal travel, until a few years ago, my family would make Plat because it would take 3-ish J long-haul round trips, which was essentially one vacation, and two family trips. Of course, I understand that these figures don't work for everyone because of location and network.

Reflecting on my benefits as an Ulti, it becomes even clearer that staying with FB makes more sense than switching to Delta. The key reason is that by switching to Delta, I would only receive the benefits equivalent to what STE+ members get on the airline I fly most often. As Ulti, I get topped up with these:

• Reserved spaces at AFKL's own lounges.
• Smooth pre-boarding in majority of my flights, even at outstations.
• Escorts through security/immigration at many outstation airports, which might not be the most familiar and make things just that extra bit smooth.
• The four upgrade vouchers that I can use at least on AFKL metal. Yes, Delta GUCs are more flexible, but again, 90% of my flying due to my location would be on AFKL anyway. Within a single year, these have already saved me upwards of €5000 in spend this year.
• Better mileage multiplier. Yes, this is minor since it only goes from 8x to 9x, but it is nice to have.
• This is inconsistent, but since 90% of my flying would be AFKL anyway, the extra attention from cabin crew and execution of preferences on board makes flying more welcoming, especially with the amount I have to fly.
• Also a bit inconsistent, but seems to work for >90% of my AFKL flights, is the neighbor seat blocking. This is extremely welcome, and I wouldn't get this if not Ulti.
• There is the faster the SkyPriority lane for immigration at CDG 2E.
• In general, staff are more willing to go out of their way to help with things at the airports. This has come in handy for things like getting a shower cabin at AMS/CDG at a specific time, while I had to take a call, and so on. It is not guaranteed, but it makes the journey nicer when possible.
• I also get access to the amazing TAs. I know there have been complaints about their lack of ability to certain things, but in my experience, they've come through for me on some oddball and complex requests. Not to mention my IRROPs experience has been near flawless (minus one last year that had potential to go south, but worked out).

Do I value Ulti enough to get 600UXP over my 300UXP (and yes, I count it as UXP, because majority of my natural XP earning occurs at AFKL)? Maybe not. But I would value it enough to push another 300UXP each year, just to get access to the TAs. Again, that's personal math. But that value would come almost right back to me in the upgrade certificates, so the math gets easier.

I understand why some other program like Delta's might be more attractive if you are not based in the core market of AFKL. It gives you opportunities to do some special optimizations that are specific to your case, and you wouldn't be flying on AFKL as much anyway since you are not captive to them as the main SkyTeam airline group in your market. But to say that Delta just wins straight up, while you want to fly as STE+ on the ST network, is not so clear cut from my point of view. It gets even less attractive if AFKL is the ST airline you know you will be flying significantly more than others.

So, yes, given the specific situation each one of us finds us in, it is possible that Delta (or someone else's) program is the best for you. But for most of the people based in Europe, who will put most of their business into SkyTeam, AFKL's FB program is likely to be the best FFP at the moment. I don't think ITA, or Air Europa even come close, due to their network sizes. SAS potentially could be good, if your travel is Nordics heavy, but I have to admit I am not familiar enough with their program to say that is the case or not.