It’s a matter of work . . .
The best part of the Inland Swap top is that it can be several machines in one. The one I’ve used was tempermental about supplying water to the work area.I used both the flat lap and the grinder with it– it worked fine.
The key questions you’ll have to ask yourself is if you are interested in grinding the bottoms of bowls or vases flat? Are you just grinding edges? Are you looking for more versatility in “sanding” the pre-fused and post-fused items?
In grinding larger areas or edges, the flat lap is excellent. For small pieces of glass, the grinder provides you more control of the glass. The grinder also allows you to grind inside and outside curves and with the different kinds of bits available– a bevel bit, a jewelry bit, etc.– it has its place in the glass workshop. The grinder is especially good for more delicate work. The next step down is probably a Dremel or Foredom with diamond burrs for super delicate work.
It’s really a matter of what you’re working with and what you might be doing in the future. I have both a flat lap and a grinder in my workshop and use both regularly. If you’re short on funds and space, a combination machine makes lots of sense.