Bike choice for Lrt trails

Hard to say, there are certainly many good options. I ride my carbon roadie (race bike) out there and it's fine.  I prefer the softer ride over what I get with my aluminum roadie (my commuter).   A bike style you might prefer is a cyclocross frame and whatever you get, something where you can roll a slightly wider tire would be ideal.   The LRT is so flat and well groomed, it's not as much of a concern as other types of trails, so I would lean more towards something more road appropriate. 

I LOVE riding my mountain bike on the trail, too, if you have room for one more bike   You obviously don't need this style of bike for the crushed limestone perfection, but I love the sound it makes.  And you can roll on/off curbs without blinking.   Then you've got a winter bike, too!

I just rode my tri bike on this for a few miles this weekend.  It wasn't awful, my tires didn't sink in or anything but it definitely wasn't as fast as a solid trail.  It was also hard to pass people since there are two sets of hard-packed trail with some loose gravel between.  I was nervous each time I crossed from one path to the other.  I don't plan on using those trails again with that bike.

I don't think it's a problem with handling, although it feels sketchy at first.   It's definitely a dust issue, though.