They are both very similar but the HonWave has a couple of nice ideas. The quality of the transon and seat come to mind.
But the biggest difference will be when you come to sell it, HonWaves are developing an excellent reputation and following, used ones sell for nearly new money on Ebay, Prowaves dont.
If you are going to keep it for 10 years ( the life of a PVC Sib) then save money and buy the Prowave. If you think you will want to change or sell it, go for the Honwave.
Had a quick look round on the web and found T-35 AE-2's for around £800, even with a nice set of wheels and cover it should only be £950 ish.