Have you considered buying a membership here on RR? You get a lot for your money, and you'll no longer be limited to using Sentinel. That in it's self is worth it! You'll also be supporting the cause!And you still need Sentinel if you want to do free database updates.
ARC536 is a good supplemental tool. Sentinel is still needed to update the full database, edit profiles, perform the occasional/rare firmware updates - pretty much anything beyond Favorites List editing.
I'll use ARC mostly for Virtual Control/logging purposes and to "pretty up" Favorites Lists, such as changing the case or justification of tags. It can also arrange Quick Keys a little better than Sentinel.
The big thing to remember is that if you edit a Favorites List in ARC your Sentinel version of the Favorites List won't have those changes. To keep them "in-sync", once your program the Favorites List to the scanner, you should use the "other" program to read the Favorites List. That will keep them identical in both sets of software.
My suggestion is that someone needs to get a good handle using Sentinel before using another brand of software.
YES!!! PROSCAN is the best in my opinion.It's excellent, yes, but 'the best'? That's subjective. Everyone's needs and preferences are different. I have ProScan and ARC-XT Pro, and use both. I wouldn't be willing to do without either one.