Ah, the ubiquitous "popularity contest" thread.
The best approach/upshot disc should be a slow disc that you can easily work on all types of shots including (but not limited to) hyzers, annies, rollers, overhands, forhands, backhands, flex shots, trick shots, etc.
The easiest way to find a disc like this is to buy a new relatively neutral putter like an Aviar P&A, Magnet, Omega, Voodoo, Ion, etc.
The preferred way- but much longer way- to get this type of disc is to beat in an overstable putter like a BB Aviar, Wizard, Challenger, Rhyno, Banger, etc. Really beat overstable putters are truly beautiful.
Putters are something I've always changed frequently. Most of the discs I listed above have filled the main putt/approach/upshot role in my bag at some point. Right now I am using the DX Polecat effectively.