I agree with the above
You can't both have a main residence
and you or the tax man will deem one
However....if you put in separate names and sell one, you COULD still get relief two lots of capital gains by formally transferring to both names, the night or week before you complete can't you ?
How would it affect your taxes
well you both have House 1 as the main residence, so no tax relief on that. House 2 if you are letting it,then the income is only declared on the owners tax form
and this might make sense if owner 2 pays top whack 20% tax and the other one 40%
so yes....there may be a tax advantage