well, i've only handled the Streamlight Jr luxeon, but i own the Gerber LX 3.0, so here is my possibly unfair opinion...
i believe the Jr luxeon has less throw, altho comparable to, and less overall light than the LX 3.0, but the LX 3.0 probly weighs over twice as much as the Jr luxeon, with an extra battery in length and an extremely heavy duty body. but the LX 3.0 puts some serious light in your focal.
personally, i have no preference between clicky and twisty, since i've found that all twisty lights i've had, i can use one-handed just fine, including the LX 3.0. but if you wanna keep it in your pocket while you walk around the garage, the Jr luxeon is way more pocketable and versatile with its small AA Minimag size and its clip.
i think it's pretty safe to say the LX 3.0 is far more rugged than the Jr luxeon too, altho i didn't get a real feel for the Jr luxeon. the powder-coating type of finish on the LX 3.0 is alot tougher than i thought it'd be, but others might be less impressed.
my favorite part of the LX 3.0 is the fact that it will be putting out light long long after you've had to change the batteries in your Jr luxeon, probly numerous times. in 3 hours (ymmv) when the LX 3.0 hits 50% brightness, it should still be brighter than, or @ least on par with the Jr luxeon.
i also think the LX 3.0 is way more purty than the Jr luxeon. but if i had to make a reccomendation for garage duty, i'd have to say go with the Jr luxeon. it's about $10 less and will ride easily in pretty much any pocket on your work clothes. it also wont weigh your pockets down like the LX 3.0, which really does have a surprising heft to it. but hey, personally, i like that.
Edit:
also, Streamlight says rechargable batteries shouldn't be used in the Jr luxeon, and any damage that occurs while it's being run on rechargable or lithium batteries will void their warranty. not sure what Gerber's stance on rechargable batteries in the LX 3.0 is, but i know they say not to use lithiums.