You can try our demo by downloading from website and compare. I don't really like product comparisons, but Realviz has not updated their retiming technology for a while now and they are probably not as complete, fast and precise as ours. You be the judge though.
I tested both (plus a few others) and we settled for Twixtor. IMHO, it's the best.
Realviz comes second, just forget the rest. If you are considering HD, Twixtor is cheaper though, Realviz is charging you premium for anything larger than SD.
Plus, you get excellent response straight from the developers here in this forum, try to get that from Realviz (we own and use other programs of theirs).
That said, no motion vector approach at this time is as good as a true slo-mo shot. To get it as good as possible, you'll need to dig into the set of tricks explained here in other recent threads, masking in particular. To own FieldsKit as well can be helpful if you are shooting interlaced. Try and generate a higher number of progressive images first, Twixtor llikes to get as much food as possible.
Hope this helps,
P.S. I'm not affiliated to RE:VisionFX, I'm just writing about the stuff and like their produtcs.
Author of "DVDs gestalten und produzieren", a book on professional DVD-authoring in German.