The key point in your comment is that you're looking at a "small 5er". Most rigs with 50amp service are wired that way in case you want to install a second air conditioner. The second AC is typically needed on larger fivers because they have more cubic feet of air to cool. On a smaller FW, this should not be needed and 30amps of service will meet your needs.
On our last FW, it was a 29 foot Keystone Cougar with one slide. We had 30 amp service and it was plenty to run the AC and the microwave at the same time. Having one AC was fine with that rig. It cooled effectively and quickly. Our current FW is 36' long with three slides. We tried getting by with one AC, but it wasn't enough in the Southern USA in the summer time. Since we have 50amp service, we installed a second AC, and now it cools much better when both of them are running.
Having 30 amp service in a smaller FW is fine, won't affect resale value and will meet all your needs. And another benefit is that the cord is much easier to handle than a 50amp cord.
Jim