necessity of Apple/Android hardware for dev and test ?

Assuming that you are an advanced WinForm programmer, and you have an opportunity for a contract to build an app (not a game, but lotsa charts, graphs) that will need to run on both IOS and Android platforms of varying screen-sizes and resolutions, as well as Windows:

1. What's the cost/benefit of having "native" hardware for dev, for test. What do you lose if you rely on whatever emulators are available ?

2, Assuming "native" hardware is really essential:

2,a, Apple: what's a reasonable hardware spec ... cpu, ram, monitor res.

2.b. Android: same question

thanks, Bill