lapua,
Talking recoil, the 500 NE is a big step up from the 375 H&H.
The 450-400 is mild in recoil compared to a 500 NE.

The 450-400 IMO is a better choice for an all round rifle than the 500, plus 450-400's are the flavour of the month right now so you could most likely sell it off without too much trouble if you wanted more gun later on.

That said, the 500 is a wonderfull cartridge and despite my "4seventy" handle, the 500 Nitro 3 inch is my favourite big chambering in a double.