I had the Tyr bag but replaced it with last year's Zoot bag. I haven't actually used the Zoot yet, but the things I like best about it so far are:
1. The overall bag depth is smaller - it sits closer to my back and teh compression straps pull it even closer. This helps since it's closer to my center of gravity and I don't have to bend forward to avoid being pulled over backwards. The Louis Garneau looks deeper, similar to the Tyr.
2. Lots of pockets! The Tyr didnt' have enough organization for me, and the interior mesh pockets didn't seem as logical - what IS that pocket on top of a pocket for? The Zoot has a panel in the most outside section with lots of pockets that help me with my organizationally challenged self. There are two shoe pockets for running and cycling shoes, the helmet pocket outside actually works - yup,lots of pockets.
3. It is comfortable - the straps fit me well and are well-padded.
4. It is BIG - plenty of room for whatever I need.
Things I don't like as well about the Zoot:
1. It is BIG! So, this is also in the good category but this thing is huge. It's a little embarrassing just how big it is!
2. Not sure yet about the clamshell design. It opens sideways like a book and I think the compartment for the wet stuff is in the very back. I'll have more of an opinion after I've used it for an actual tri with all the associated nerves that go along with it.
3. The expense. I justified it with two facts: one is the fact that I spent so much on my other gear that this is just a drop in the bucket. The real one, though, is that I hope to be doing this for a long time, and even though I will upgrade my gear over the years, I want exactly the right bag starting now!
The Tyr is also a fine bag with lots of good features - love the zip-out, drop-down wetsuit pocket on the bottom. I just found that the Zoot fits me better.
Good luck, CC
P.S. why don't the sites show any of these bags OPEN!?!?? That would be a big help.