what's the actual difference between ipad mini 2 and 4

the one i m using is mini 2 which was bought quite some years ago

I've tested it in the shop together with ipad mini 4

otherwise than the touch ID I cannot see significant difference in terms of the hands on performance

opening safari, mini 4 is less than 1 sec faster
anything else, mini 2 shouldn't be very much lagged.

To my surprise, the mini 2 in the shop is the most updated iOS version


however, my iPad mini 2 is very lagged for most applications. The current version is still iOS 7
which I suppose should be faster than iOS 10 because 10 may require more hardware resources.

1. Should I buy a mini 4 ? or should I wait for new mini that may be released later.

2. Should I stick with my old iOS 7 or update to iOS 10?

 

Unless price/budget is a matter, I would hold off on getting a Mini 4 right now. I saw some good deals on Black Friday but I held off. I would've gotten a Mini 4 if it didn't use the old A8 chip (iPhone 6 generation). They use the A9's in the iPad Pros, but I am hoping the next refresh in the Spring of 2017 sees a Mini 5 with the A10 chip. Would buy day one.

Can't help you with the iOS 7 v 10, I always update that right away, can't help myself.

 

The update from A7 processor to A8 was marginal at best. The real leap came from A7 to A10.

Never update your iOS beyond the same major version it came with. Never full restore it through itunes, it will require you to update to the latest firmware. Apple does this in a form of forced obsolescence, as the new firmwares pack in too much new stuff for old processors and RAM to handle, and they will never let you downgrade back to iOS 7.