IMHO Gold is the sweet spot for UA. You'll get all the priority benefits of *A Gold, lounge access, priority everything, E+ seating for you and a +1 at time of booking, etc. Sure Platinum gives you slightly higher odds of winning the upgrade lottery and 2 RPUs which may or may not be useful to you. But for all intents and purposes once you hit Gold you're Golden! IME flying UA long-haul I'll just say that not all E+ seats are created equal. There are some seats (especially on the 767s and 777s) where you get ample legroom to the point where you can have a window seat and get out of your seat and into the aisle without waking anyone else up. I agree that the slimline seats aren't great. However, this seems to be a trend most airlines are adopting (i.e. look at the fiasco AA is in with their 737MAX planes).

That being said, there is an argument to be made for being a free agent, especially on those long haul flights. Sometimes you can find a great J deal with lie-flats which are only marginally more than what UA is charging for Y! In which case my loyalty for UA/*A goes away, especially if I'm already on target to hit 50K miles and 4 UA segments for Gold. You may also want to research upgrades and how to improve your odds of getting them on UA flights since J/F long haul service on UA is pretty good (especially with the introduction of the fabulous Polaris lounges domestically). There are numerous members on this community that have secured upgrades for their long hauls flights months out, sometimes at the time of ticketing! IMHO this is one of the few benefits of UA's program is that they offer numerous ways to upgrade and numerous ways to improve your odds of upgrades clearing (i.e. using Expert Mode to find routes with R availability).

Speaking of MilagePlus, one thing you want to think carefully about is which milage program to belong to since they're not all created equally. For instance, Asiana's Club allows you to get up-to 4 years of *A Gold by flying just 50,000 miles on Asiana and *A partners. The caveat to the program is that milage accrual isn't as lucrative if you're booking into the lowest fare classes (i.e. STLKG on UA). In addition you won't have access to UA specific features like CPUs or free E+ seating. OTOH you'll have access to benefits that not even Global Services elite have access to like use of UCs when travelling domestically since you belong to a "foreign" *A program. In addition, you can get lifetime Gold with Asiana by flying 500,000 miles on Asiana and *A partners. That's a huge reduction to the 1,000,000 miles on UA metal that MilagePlus requires for Lifetime Gold.

Are there ways out of the PQD requirement? Yes! If you're not a resident of the US (i.e. you reside in Canada), then you don't need to worry about PQDs. There are also some credit cards I hear which waive or reduce the PQD needed to spend. Finally, you can purchase tickets issued by UA which are operated by another *A partner (called codeshares). So for instance, you could fly NH from SFO to NRT or LH from SFO to FRA with it being ticketed by UA to earn PQDs. IME NH and to a lesser extent LH have a better PE service than UA's E+. Of course we'll have to see what UA's PE offering looks like in the coming months. Hopefully it doesn't compromise the E+ availability service (i.e. infinite legroom) since I'm a cheapo and for me UA has the cheapest fares for long-haul routes out of YOW/YYZ.

Hope that provides some insight.

Safe Travels,

James