Generally, the Tricaster products have all the bells and whistles, including the kitchen sink and all the plumbing. But VERY software and computer system dependent and not inherently as reliable as a one-piece, all-hardware solution like ATEM.
Features: Tricaster wins (if you need all that)
Price: BMD ATEM wins (unless you must buy extra hardware to provide other features)
Reliability: BMD ATEM wins (although the newer Tricaster stuff looks like they are getting better than glorified PC boxes).
Size: BMD ATEM wins (again, unless you need more features that take space, like recorders, etc. etc.)
I would much rather rely on an ATEM on the road than any Tricaster (which are essentially very fancy PCs). Although the more recent Tricaster models seem to be more industrial-strength.
IMHO, it depends A LOT on exactly what your requirements are and how they fit what is available from Newtek or BMD. Since you provided no details, we couldn't even guess how that decision would fall.
Note that Newtek is doing an interesting panel discussion at NAB on Tuesday evening.
http://www.newtek.com/nab2012