I suggest that you contact all three through their websites & get a quote (don't forget to see if you qualify for any extra discounts such as AAA, senior, Amex or other credit card discounts, etc.) & then wait around two days.
I found that the companies will email you a follow up and they often include an extra discount at that time.
Also, depending on how far you are moving and if there are multiple locations to pick up & drop off that are convenient, check the differences between the local rental & their one way rates.
I offer home staging as part of my services and rent trucks often & I usually end up at Penske and sometimes Budget. Uhaul I found is more expensive, their trucks don't seem as nice, and I find that when I do use them (like when I just need a small trailer) at their stores (not the little dealers that are also businesses like storage units) they are always understaffed & we have to wait to get served.
Another tip, if you are comfortable haggling, is after you get your quotes call around to the actual pick up locations and see if you can beat it. (This usually works better if you are using a competitor's quote).
Best of luck,