A dolly is likely to be smaller in width than a trailer, a trailer is much easier to deal with and can be backed up where a dolly can't. ( The ball and wheel pan pivot making for a messy backing up. )

How far do you need to go? If over 100 mi you can get a high mile / business rate. Something to know, company stores carry all equipment but independent stores generally only have box vans and small enclosed trailers in stock.

Don't reserve on line if you want to pick up at a independent store, go the the place and talk to them. I rented a truck for a 800 mile round trip. They only charged me for 1 day even though the pickup / return was 1 1/2 days , gave me a really good mileage rate and a new sub 2,000 mile truck.

They were a towing company / car lot and the owner was excited that I was picking up a frame machine for an interesting project.