For those interested: I'm a heavy user of laser-cut acrylic templates. I've tried many different companies and material thicknesses over the last few years, so let me throw my official (however little weight they may carry) recommendations out there:
For the best balance of usability, durability, and price, go with 3/8" acrylic. I've found 1/4" to be too flexible and prone to melting, even when used briefly as master templates. I love using 1/2", but they're just overly expensive for little real benefit over a similar part in 3/8". I'd say 1/2" is really only worth it if you need something to be extremely sturdy...like the adjustable sides of a Myka jig, maybe.
And for places with lasers, my best experiences and results have been from Pololu's custom laser cutting service. Very fast, reasonably priced, and most importantly, totally accurate. Just make sure your drawings have accounted for the laser kerf, which is about 0.005" in Pololu's case.
Happy lasering!