I mostly choose Revenge because Roman dying is just way too heartbreaking for me, especially on his wedding and while Mallorie is pregnant.
But overall considering IV's tone and the overall story I do think its a bit more fitting than Revenge. Dimitri also makes a better final antagonist than Jimmy (who we just met in the last act)
Revenge feels better because its "just" Kate who dies. Don't get me wrong I like her a lot and its still sad that she dies but nowhere near as Roman's death in Deal.
I also like it better that Niko deals with Dimitri and Jimmy Pergorino personally in the Revenge ending missions. In Deal Jimmy meets a rather lame end
I was just playing GTA IV once again (the sixth time I think) and thinking about which ending to choose this time