In general alps would have beter snow, caus they are higher, bigger resorts and therefore more runs. However a lot more expensive. I've been to alps and Bulgaria. If the snowwas a bit more reliable i'd choose Bulgaria. Tuition excellent in Bulgaria.
We are trying Bansko for the first time this year as we are taking the kids and needed somewhere cheap - So I am reserving judgement at the mo - But Personally I would never go back to French Alps again (Courchevel) - Very over-rated and expensive - We are Andorra fans - Soldeu especially - Totally fab and half the price of the Alps - Although like most places they have suffered thru lack of snow this year - Bankso will need to impress to steal us away from Andorra