Welcome to FlyerTalk, andiruleu.

Please explain what you mean by "in conjunction". Do you mean using an SPG Amex at Hilton HHonors hotels? Or do you just mean holding both cards and alternating use of them on everyday spending? Or what?

In my case, I always have a card for most of the hotel programs I belong to, including Marriott, Hilton, IHG, Choice, and Best Western. I use that card on stays in that program, since it earns way more points in that case than anywhere else. I also use the Marriott and IHG cards as my primary cards on trips outside the US, because they offer 0% forex (which none of my other cards that I always* have do).

*But other than for these hotels, the cards that I always have take a back seat to whichever card I've just applied for on which I have to spend (cumulative) $$$$ (within the first N months) to earn the big miles or big hotel points or whatever. The miles you earn from signup bonuses are at about 30x or 50x or so of the miles you earn any other way, to the point that if you apply for several cards a year, the earnings you'll make from the signup bonuses will dwarf all the other earnings you make from "normal" card usage (unelss you have, for example, high business expenses).

I'm not a "big" churner by FT standards, but right now I'm working on the $2000 cumulative spend on a Chase BA card that will give me 50k BA miles, and before that I was working on the $1000 cumulative spend on the Citi Hilton HHonors Visa that gave me 60k HH points (that offer is gone, it's only 50k now), and before that I was working on the $2000 cumulative spend on the Chase UA card that gave me 50k UA miles, etc. (And yet for my Marriott stays I was still using the Marriott card, and for my Best Western stays I was still using my Best Western card, etc.)

Or sometimes I'm working on targeted promos, like earlier last year I worked on $600 cumulative spend on an existing Citi AA card to earn 2 Admirals Club (AA lounge) passes. I used on one of those lounge passes on a Christmas flight where I had a 4-hour layover at DFW which turned into 7ish hours after the connecting flight got severely delayed. Or last fall I worked on 50 individual purchases within 6 weeks (it was officially 2 months, but they were 2 weeks late of notifying me about the promo!) for 2500 bonus LAN miles on my US Bank LANPASS Visa.