Can I ask what you bought in the end?
As I currently have the RP1 and I'm considering buying the RP3 but reading this thread it doesn't like worthwhile?
I bought the RP3.
I must say, I did have some problems with the RP1. The platter had the "wobbling" issue and the tonearm drifted a bit when the needle did not touch the record.
The RP3 did not have any of these issues. I think it was a good overall upgrade: The platter feels more of a quality product and also the tonearm "feels" and works better.
The audible difference is something that is hard to describe. The cartridge is the same as I had with RP1 (Ortofon 2M Red). But I do think the sound is more "fuller" and at the same time precise. I did not expect huge improvements regarding to sound right away, but it seemed reasonable to upgrade the turntable first and then upgrade the other parts of the system including the cartridge and phono stage.
I would upgrade again, if I had to make the decision again.