Best pump and why??

Direct drive is stronger but unforgiving. Most operators require an overfill shutdown that's harder to wire than a hydraulic cut off. Unless you're talking about water then direct drive all the way. Never know when you'll have to suck water out of the top hatch.

As for the brand, depends on what area you're working. See what the locals are doing

 

I'm retired now but all I ever saw in my part of the country was Roper's, and most all the shops around that worked on crude trailers would have parts (either new or take-offs from older pumps laying around) . And yes because of the overfill protection, hydraulics is about all I have seen in quite a few years. Another option to consider is whether to have mechanical seals or packing. Both have their pros and cons and I think I have seen them all.