I recently replaced by SRAM NX/GX 12sp with an a la carte Shimano 11sp package and went from the worst drivetrain I've ever used to the best. I was running an NX shifter/cassette with a GX derailleur. The chain drop on backpedal drove me bonkers. It's simply not acceptable on a bike that's made to ride up mountains. Plus the shifting was pathetic. This is after many trips to the LBS where I bought the bike.
So now I'm running an 11 speed system with 28T chainring (same GX cranks but replaced a 30T with a 28T) and a SunRace 11-46 cassette (Shimano 11sp cassettes have too big a gap to get into the big gear).
I've got an 11sp SLX derailleur and splurged on an XTR 11sp shifter for all the fancy shifting options.
This new setup is awesome. No chain drop. Crisp shifts. All the range I want (without a big heavy pie plate at the back).
Happy as heck to be back on Shimano - an old trusted friend. I find no negatives to having 11 gears to choose from rather than 12.
One thing that surprised me was that the old GX 12sp derailleur was 29 grams lighter than the SLX 11sp.
But the old NX cassette was a boat anchor compared to the SunRace so the new system is lighter.