Some other stuff that VTTs have that MapTool doesn't:
Roll20 has: a marketplace of free (and paid) professional art, subscription levels if you so desire (which brings extra features -- I
do consider it a weakness however that dynamic lighting is only available to paying subscribers); tablet and mobile device support; built-in asset searching as well as your own library; card deck support; built-in music and sound effect support; an API coming down the pike; and like Fantasy Grounds visible dice rolling (as well as -- finally -- an obvious "here's where you roll dice" feature, which is something MapTool
still lacks). It also has Google Hangouts integration, if you're into that sort of thing.
I don't think I'd call Roll20 a "beginner" or "starter" VTT; it's a complete solution and what I intend to use when I crank up my next campaig, and I'm certainly not a novice. In fact, I think the "starter" moniker reflects a certain pervasive elitism regarding MapTool ("cute software, kid, but when you grow up, use a real VTT") that isn't really justified anymore.
Fantasy Grounds approaches the entire concept a bit differently; the shared map is just one element of the "stuff" on the table in FGII, while in MT, Roll20, and most other VTTs the map
is the table. They're harder to compare. But again, as a gaming tool, they do make dice rolling
very obvious and from what I hear frameworks are
very good. Plus, sharing of handouts, books of data, etc.
Infrno is more of a shared whiteboard that supports gaming conventions, but for certain games (namely, games where a map doesn't matter) that can be better than anything else out there. Of course if you don't need a map, I don't guess you'd head toward "MapTool" anyway.
There are a number of up-and-coming tablet-based VTTs too, which are completely outside of MapTool's capabilities, but I'm not really sure how many groups are going tablet-only or anything like that.
Also, while feature-by-feature comparisons are useful, it's also important to consider the overall impact of the tool. With regard to a "complete package" viewpoint - ease of use, resources, development, features, look and feel, user experience, and so forth, I think MapTool lags way behind.