Snowdonia and size of caravan

LineV

Hello,

I am taking the family from France to Wales (Snowdonia) one week this summer. I have rented a motorhome, a 7berth was recommended for comfort as we are five persons travelling, which is 7m's long and 2m12 wide. After reading a bit about the roads in Wales
around the Snowdonia area I have doubts whether I will regret travelling in such a big motorhome. Should I rather go for a 5berth or is the difference in size not that important that it really matters. Any part of Snowdonia I should avoid with a motorhome?
thank you for your remarks, KR Line