Here is a link to a thread on the BG forums that makes some comparisons between Battlegrounds and Fantasy Grounds. It's somewhat dated, mind you. If you do a search there for "FG" and/or "Fantasy Grounds", you should find a number of relevant discussions.
Here are some recent quotes from other threads:
"After purchasing Fantasy Grounds and being rather disappointed in its GUI I came to better appreciation of the interface Battlegrounds has and how vastly superior it is to Fantasy Grounds. There is something to said about practical versus glamorous."
"I feel much better in my purchase of Battlegrounds over FG. I kinda want my money back with Fantasy Grounds. It's very disappointing in my opinion. It's like a bright shiny red Ferrari that's next to impossible to drive."
As for a comparison with Scene Grinder, it's hard to say without trying out Scene Grinder for myself. Battlegrounds has a free Demo, as do most other commercial virtual tabletop programs. Perhaps the folks over at SG should consider giving anyone that is interested a free 1-month subscription, so that they can evaluate the product in actual use, rather than having to rely on screenshots and video clips when making their purchase decision. That would also allow them to establish a decent userbase and get some feedback going on their forums.
Based on what I was able to glean from the SG website, it seems to have a lot in common with Battlegrounds: it is cross-platform, has a strong focus on the map (nearly full screen), nice visuals, appears to be RPG-system-agnostic, has animated token moves, and it can handle rounds/turns/phases/segments. (the last two features are uncommon in VTs)
Token support doesn't seem to be as extensive as Battlegrounds' (no token-swapping for changing poses, no variable base sizes, etc.), and it doesn't appear to handle audio at all. Not sure about visual aids. Perhaps these things will be added later, but nothing on the site indicates that the featureset will expand over time.
Still, it's an interesting new VT offering. I doubt the subscription requirement will be a big draw, and I suspect the monthly rates will need to come down if they want to grow the userbase.
