It totally doesn't matter.
If you choose to go with a pool that has a high hashrate you'll get rewarded more frequently with smaller amounts as blocks are found in less time. But if choose a pool with a smaller hashrate, you wait more until a block is found and then the reward is big (but actually the same.)
Most of these pool use a system called PPLNS which totally depends on the number of shares that you submitted until the block was found. It is totally the same.
Thanks for the replies again, I've been switching between the official pools, hashparty and easyhash, keeping an eye to see who finds the blocks.
Currently I'm mining electroneum and I totally prefer pools with a lot of hashrate. Not for anything specific but just to be able to jump and leave if I decide to stop mining the coin.
Also, can someone explain the difficulty when joining pools please, is it a good thing to join using the higher difficulty port, do you get more reward if you do?
No. Doesn't matter. Put it on the middle one.