I fly Emirates from the US to Europe and back a few times a year in J on A380. I far prefer it to UA F or J. Some comparisons:
- EK includes car service on both ends
This is a great touch. And the fact it's offered in so many cities to both F and J customers without making them jump thru hoops is fantastic.
- UA has nicer ambiance in the GF lounge at SFO, but there are far better F&B offerings in the EK lounges. I was last in the UA GF lounge in March and was told they would not get out Veuve until whatever prosecco they had was gone. EK offers a full self-serve bar as well as Veuve at minimum. EK's food is plentiful - full buffet dinner offerings. Quality is average; it's not the LH F lounge, but it's not bad.
UAs GF lounge in SFO is unfortunately the only quality lounge UA has in the US. But as you mentioned the F & B offerings are a joke in this day and age. What's nice about the EK lounges outside Dubai is the CONSISTANCY. I know that regardless of where I am, be it Colombo or JFK, the lounges at EK will pretty much offer the same product with the only real difference being the local cuisine changing. But where EK really stands out is the F lounges in DXB. I find them as good if not better then even LHs F terminal but that's a personal preference that can be argues to death. It depends what's important to you. A private car to the gate is nice but IMO boarding from the lounge is even nicer. The fact that EK has quality chefs in the kitchen 24/7 that will make you what you want, when you want can be a big help. I find UAs cold cuts and fruit to be a little insulting coming from a carrier that wants to fly people non stop from SFO to SIN (although I guess that flight doesn't even have GF
- EK generally offers boarding from the lounge in MXP
As well as a number of other cities. I am however very disappointed in the hap hazard way that EK has taken over concourse C in DXB. I landed in C a few days ago and even as an IO, had to hike to the buggy waiting for me. That is a heck of a long walk between the further gates in C (which was designed to go with T1) and baggage claim at T-3
- I don't get pre-check flying EK since they are not a participating carrier. Fortunately, I get a premium line, so it's shorter. I would not fly EK if I had to stand in the regular TSA line.
That can be a deal breaker as the TSA has made such a mess of things that flying out of or within the US has become a horrible experience (even sometime with pre check or an F Boarding Pass. But the fee for CLEAR is with every penny if your flying out of SFO, and as an IO, I'm walked thru security at JFK. The TSA is really a big reason I WILL NOT fly UA any longer. T-1 @ JFK for LH flights works better then most. But I would not for the life of me go thru EWR even with pre check and gamble on what the day has in store for me
- Wines and alcohol on EK are superior to UA. On-board bar on EK. EK makes me perfectly acceptable Manhattans.
Here you can't even compare the 2 airlines. The amount of time &money EK puts into selecting it's wines can't be matched by any carrier flying today (IMO), I'm not a fan of champagne, my drink has always been cognac. Most carriers serve excellent XOs in F, UA can't even load enough little VSOPs to last a flight more then 6 hours (I have not seen a VSOP in F on any carrier for years except UA........but then of course EK offers Paradis which they proudly call the "most expensive drink in the sky". That's actually a silly waste of money as at 35,000 feet I dare anyone to really tell the difference between a good XO & Paradis....but even the Whisky offerings on EK, which I'm no drinker of either is impressive. Blue Label is pretty standard now among quality carriers but it's nice that EK offers not only that, but 2 others if Blue Label isn't your thing. What's UA serving in GF? Red Label or that label no ones ever heard of?
- I request vegan meals on EK and receive beautiful food. They are the only carrier I get this on. UA has horrible veg meals.
They do consider India one of if not its largest market 
- Personal minibar on EK means FAs don't come around too often with water and beverages, but it's at my seat or at the full bar in the back.
This mini bars in F and J are a waste of space. I just don't get them 
- FAs on EK are quick to pick up glasses rather than refill them. I find I need to protect my glass from the minibar or lose it.
Never heard that before until yesterday........ interesting, your the 2nd person to say that
- Amenity kit on EK is Bulgari. Larger lav on EK.
I love the EK kits as I actually use the stuff (like the shaving cream, razor, tooth brush. Are the LAVs in J really bigger?? The LAVs in F on the 77W seem the same size as UAs to me but then we come to the 380!!! The SIZE of those LAVs including the showers always makes me smile
- Entertainment- I don't use much, but EK has the cameras mounted on the plane so you can watch takeoff/landing.
I don't use it much either but with over 2000 channels, there is something in there for everyone (in almost every language). I must admit I did watch THE ENTIRE first Eason Of the West Wing on a flight to LA
- I generally prefer EK's FAs, but they are not without lapses. They sometimes gather at the bar and chat.
That doesn't bother me. AFAIK they can chat away as long as they are there when I need them. I've been lucky w the fact in the 19 years I've been flying EK (13 of which I've been based in DUBAI, I have NEVER EVER had what I would call a "bad crew". Of course some are better then others but "bad"?? NEVER. ....On UA I have had some wonderful crews, but I've also had crews that have made me seriously consider locking myself in the lav for the entire flight. I admit it's not the norm but it should be NEVER!!
- I have no complaints about the seat/bed on either carrier. I like the privacy of the seat on the side on EK.
If I was in J I'd take UA over EK on the 77W, on the 380 I'd take EK and in F EK always wins on any aircraft
- EK offers wifi for $1, but it's slow and buggy. UA's more expensive wifi works much better, ime.