Hi,
Both choices are good ones, I would say the Kind of antenna is very important. Look up GMRS antennas on amazon, also look at YouTube for some tips as well. I sure some of the other Radio Experts (in my opinion, Great people by BTW) on here will give more feedback to this question, but I would say a repeater even if it's the portable one: Amazon.com: Retevis RT97S GMRS Repeater, RT97 Upgraded Version, Radio Repeater, Full Duplex Long Range, Compatible with Raspberry Pi, Portable, LCD Screen(1 Pack) : Electronics
I understand you are budgeting things out. just put this on the list this can maybe be deployed in the event of a storm and then you can cover the 20-mile gap.
I'm just thinking of Quick deployment scenarios.
I'm also New to GMRS.