I use both ARC and Sentinel. Like most any software packages there are pluses and minuses.
ARC will do some things that Sentinel doesn't, such as change the case of tags to upper case or centering the tags.
On the other hand, ARC won't update the full database or allow you to work on profiles.
So for me, it comes down to what I want to do. The trick is to coordinate the files. If I change something with ARC, I'll write it to the scanner, then read it back into Sentinel and vice versa.