I'm late to this party... lots of great info here already, but here are a few comments.
1) When I was competing in Production with G34s, I found 147gr bullets to be significantly more accurate than any other. There's also the advantage of it being very easy to make minor power factor with 147s. When I switched to a Sig p320, I found that 125gr bullets were superior to the 147s in those guns.
I have seen issues with accuracy and ejection using 115s in Glocks, and I just don't like the feel of them either.
Before my buddies dumped their M&Ps, the worst vertical stringing happened with 115s.
Yesterday's match: a dude bought some cheap 115gr ammo for his G34 and discovered that now he couldn't hit small targets. Half of his shots were 6 to 12" high. He was incredibly frustrated.
2) I'm using 125gr Bluebullets in my Shadow2s.
3) No. Just more QC.
4) I like the new Federal Syntech 150gr match ammo.
A buddy is now shooting a Q5 and is kicking ass. He's found them to be very reliable. It does not fit my hand (strong hand middle finger knuckle hits sharp corner of trigger guard), but it really works for a lot of folks.