The # of apps only matters if the apps it lacks are ones you would need. App wise I would have been fine buying a WP7 device over my Android phone, but the problem for me with Windows Phone, was not the apps or the operating system, which looks superior to Android to me. But rather the total lack of high end devices, and the lack of any decent device on Verizon.
A subsidized cell phone is a ~$2000 purchase. To me buying a $50 or $100 device is like buying a year old laptop for $1900 instead of a brand new laptop for $2000. Or if you just get your phone off Amazon's 1 cent sale, they cost the same.
So going WP7 over Android, I'd have ended up with a mid range handset with a 800x480 screen, on ugh ATT, instead of my Rezound with its 1280x720 screen on Verizon LTE. Which made going Android the obvious choice for me.
If WP7 would put out high end phones with cutting edge features like high resolution screens on Verizon, then I'd be definitely interested in switching in 2 years. Or hell since my Rezound has a snapdragon SOC, if they could get HTC to sell a rom of a WP7 release that makes use of Dual Core SOCs and 720p screens id buy it for $50.