Seems like this gets asked a lot, but of course I can't find any of these threads in the LS forum (maybe upstairs in the Modern Era forum). Anyway, depends on who you ask, what you want, what you play, what you're willing to haul, etc. Need more specifics about what your situation is. My take:
Express is easier to haul around and will do something closer to hard rock/metal as well as provide a decent clean tone. If I were in a hard-working cover band I'd probably go with this amp because it has some nice easy-to-dial tones out of the box, clean and dirty. And it's about 20 lbs lighter.
So the Lone Star is heavy, but is more powerful and has a better/more versatile clean tone, and a really fat singing lead tone. Very responsive and touch-sensitive. Not as good for hard rock and doesn't do metal at all, but it's a terrific amp for classic rock/roots/R&B/funk and anything that doesn't need a really hard-edged Marshall crunch. If you just want saturation, the LSC has tons of gain; it just isn't voiced like a Rectifier, more like a Mark I.
