I think you pretty much answered most of your own question in regards to the differences between Gwaltney and Rennick. The amazing thing about this activity is the differences you will find from corps to corps. I think the only way to really judge solely based on talent would be if every line had the same book and technique (Cadets use a different grip and stroke compared to PR, SCV, Cavies, etc). You touched on one important part, and that's the musicality of the book. I personally saw this bigtime in SCV between 2004 and later years after Murray left. The 2004 book was a night and day difference from some of the others. Unfortunately (well, in your case since you're a PR fan and I'm a SCV fan ), the idea of moving from corps to corps as a member can lead to one corps having better talent than the next. However, this is also a good thing because that means students and corps members will always demand top talent for teaching, which obviously leads to overall better musicians.