eyepiece choice

I have found a particular brand and style of eyepiece that is basically perfect for me. I have only the 25mm eyepiece which currently I use 100% for my visual LPV observing. Now I have seen discussions where observers talk of having a range of powers available to them useful, I assume when one is working very close to the scopes limits.

So anyway I am in a position to purchase one more eyepiece, so I am wonder what the seasoned observers would suggest. I have the choice of 18mm 15mm 12mm 8mm or 5mm. Personally I am thinking the 15mm or 12mm - but what do you say?

Thanks Glen