Either or, it doesn't matter. They all do the same.
Buy a Nokia or a Sagem.
2x Flash chips will flash faster than 1x but they work the same afterwards.
Make sure the box has 32MB of memory. Any less and you won't be able to use it to watch pay tv.
Some boxes come with 'stripes' on the lcd. It's merely cosmetic and the menus and stuff come up on the screen but it does display the channel name and time so it can be useful. Try and buy a box with 'no stripes'.
Nokias have a reputation of being 'better built'. But all the components are on the main board. If one part fails, the whole board fails.
Sagems are modular in build and if one part fails, it can easily be replaced.
Make sure the box is in 'debug mode'. Without this active you won't be able to flash a UK image. If it's not in debug mode, don't worry, this can be done, but it's much easier if it is in debug mode when you buy it.
Everyone has their own experiences and own opinions what box they link best. If it works, it works
My opinion - stay clear of a dbox2 and get a Dreambox