Been using a TBAC 6.5 Ultra 7 for over 3 years now, on a 6.5x47L. I have always used a 24" barrel for that little bit of length reduction.
What's your primary use? If it's comps and PRS type shooting, I would 100% go with the Ultra 7.
- You will not be able to hear the dB benefit of the Ultra 9 because you will always need ear pro on at a comp due to others shooting.
- The extra 2" of the Ultra 9 will suck going in and out of port holes, cattle gates, etc. Don't let anyone tell you otherwise, any extra length is a disadvantage during 90 sec stages with 5 positions. A typical match rig is a 26" barrel with a ~3" brake, totalling 29". A 22" barrel with an U7 would put you at the same length.
If your primary use is plinking and you don't like wearing ear pro, then the Ultra 9 would suit you well.
If your primary use is hunting, then the U7 or even U5 would be the best.
Or as others have mentioned, the new TBAC Dominus splits the difference in sound suppression between the U7 and U9, while being shorter than the U7. Biggest downside is you'll be waiting a looooooong time to get one, versus hitting the phones and finding and Ultra in stock now.