I don't have the Polybrute, but obviously it can do A LOT more modulations and programings than the rev4.
However, although I love Arturia, personally I've never been impressed by any sound of the Polybrute, whereas rev4 has got one of the best "raw" sound and a tons of sweetspots.
They are 2 very different beasts, so it's up to you, depending on your needs.
Rev4 is great for vintage/classical sounds, whereas PB is better for complex and modern sounds.