They have a free trial you know.. I would LT has some limitations but probably works just as well for most simple projects, but I am guessing and comparing it to AutoCaddLT.
It looks like the main one is that you can't do worksets. If you're a stand alone user, it won't matter. If you need five people developing the model concurrently, it's a deal-breaker. Other things don't seem to matter as much... reinforcement/trusses may be a deal-breaker as well if you're doing rebar detailing or designing trusses, though. Photorealistic rendering was the other thing that caught my eye.