The LSTs are rare and a sort of AR collector's holy grail. The LST-2s are more common but still a good speaker. My friend's father had the LST's and they were ( at the time) amazing to this 16 year old's ears. Never heard the LST2's. They were the economy model of the design-not as large,heavy or expensive as the original. AR ( at the time) claimed that the only difference was the bottom octave. Whether that was true or just marketing, I couldn't say.
If they are reasonably priced, I'd go for them.
Ray