It's going to be hard for any contributor on PPRUNE to offer you an opinion as to how Virgin views a PPL on application. They may think it's great, they may think it's too much experience for what they're going to do.
What I can tell you is that even if you have to redo some of your training during the cadetship this isn't a bad thing. I did the QF cadetship having already done my PPL. Instead of the 30ish hours required to get to the GFPT equivalent test back then I did about 15 but it was mostly consolidation rather than learning afresh. That's not to say that I didn't learn anything on those flights- quite the contrary. Rather the learning was gaining confidence in the operation or modifying slightly something i did to conform to the 'airline standard' that was we were supposedly being taught. I certainly appreciated going back to the basics and really refining my operation and it gave me great confidence in some things that previously I'd been a bit cagey about. Similarly, instead of the 9 Navs in the syllabus I did 4- all great fun- and I learned quite a bit in those that made me a more confident aviator.
So best of luck making the decision. Possibly only hindsight will show you which decision was the 'right' one.