Topher,
The 14 ft GLX 9/10 is a bit slower than the 13 and 15 ft GLX's. It does work best with the 9/10 spey lines (at least up to the mid-belly length lines, the Extended-belly GS should be downsized one line); however, the T&T 1409 is a true 9 wt (or 8/9 as most 2-handers are rated) rather than a 9/10. The T&T 1410-3 is the one that the 14 ft GLX should be compared to. The T&T 1410-3 and the 14 ft GLX are very close, the GLX feels lighter in the hand though, and the T&T 1410-3 has more reserve power in its butt. I prefer the T&T 1410-3 because it is a little faster (very little faster) and because it has more power in its butt.
The T&T 1409-3 (or the 1409-5) is my favorite 14 ft 8/9 rod. It has an action and feel very similar to the 13 ft GLX 8/9. The 1409 is a casting machine that is a joy to cast and fish with.
The 15 ft GLX 10/11 really should be compared to the T&T 1511-3 (remember that T&T rates their 2-handers with the top line number onlym thus the 1511-3 is really a 15 ft 10/11 rod). The 15 ft GLX is much lighter in the hand and is a little faster rod than the T&T 1511-3; however, the 1511-3 is a much more powerful rod than the 15 ft GLX, which you will feel as soon as you cast it. The 15 ft GLX has a nicer casting feel to it; but the T&T 1511 is much better at tossing really big or heavy flies and tips. For sheer joy of casting, I prefer the 15 ft GLX, for ease of fishing the big stuff, I prefer the T&T 1511-3. I would take the 15 ft GLX 10/11 over the T&T 1511-3 unless I was going to use it only for fishing big stuff because the GLX is a little faster, lighter in the hand, and seems to take less effort to cast.
The T&T 1510-3 (or the 1510-5) are my preference in 15 ft rods, which is why I own one. It is a wonderfuly fast 9/10 rod when used with short and mid-belly lines (lines up to about 75 ft bellly). I almost always fish it with the GS 8/9 anymore because I use the rod on mid-to large-sized rivers and use it for summer fishing on them. It is a very responsive and fast rod that is simply fun to cast.
To summarize: I prefer the 13 ft GLX, the T&T 1409-3, the 15 ft GLX, the T&T 1509-3, and for the really big stuff I prefer and use the T&T 1611-3 over the other rods of similar size and line designation.
Thanks for the compliment on the flies.