Depend on you.
If you want more apps, games, customization go for G510. Android offers more apps,games and customization as compared to windows.
If you don't need above ones go for 630. It has quad core CPU and G510 have dual core.
630 have batter resolution screen and better GPU
630 lacks front camera but G510 have Vga front. So you cant do video call/skype video calling on 630
630 is light weight 135gm than G510 150gm
630 have corning gorilla glass 3 protection.
630 have little bit bigger battery capacity than G510.
Lumia 630 is much better quality phone and for your needs it will be perfect. There are apps and games for Windows Phone platform too. For youtube, if you would choose Lumia 630, i advice you to use alternative apps, not the one from Microsoft
Touch is much more responsive and precise in Windows Phones.