Depends, there are 3 "lst's" available.
The aftershock is closest in kind to the original LST. The original LST had forward/reverse and a high/low knob. Also, the LST* two speeds are built better using an alloy hub for the two speed gear and another for the OWB. Engine was different and a different pipe/header. Tires/wheels different I think. AS has plastic threaded shocks whereas the LST had alloy with collars.
Otherwise, the AS and LST1 are pretty much the same.
The LST2 has yet another engine/pipe combo, beefier arms/axle carriers/chassis rails, no tie-rods on the rear carriers like the LST1/AS, larger wheels/tires with larger hex's and a larger capacity fuel tank with a flat pack on the bottom of the chassis. Trans was pretty much the same as the LST1. Also had threaded alloy shocks.
The LST XXL is everything the LST2 is, but longer (in the front only I think), might be a bit wider with some wheel hubs... can't recall, but also has a larger engine than the LST2 and different gearing in the trans or the diffs, can't remember which.
The aftershock isn't bad if you get the LST* two speed assembly (can find on ebay), RPM arms with lunsford turnbuckles for the upper arms (pricey, but totally worth it) and lunsford turnbuckles for all 4 corners, also pricey, but way worth it. Also, an LST2/XL pipe makes it perform far better.
I ran an aftershock. The no frills trans was a bit of a blessing, less crap to worry about. The two speed sucked which I replaced with an LST* version, I immediately upgraded to RPM arms, then quickly upgraded the tie-rods in the arms to lunsford as I broke one within my first tank. I did quite a bit of other stuff to make it stronger. I also ran non-stock tires as the stockers and LST2/XL tires are just too big for my liking. Made the truck feel like a hog. I ran revo 3.3 17mm tires. Made it far more agile.