Is there a big difference in ease of use from a "screw" type to a lever type valve spring compresor tool? Especially considering room under the hood. Looks like there will be some fuel lines to deal with. Can either of these be used to do a one-man valve spring job?

Lever style is quicker and easier although they will both get the job done.

I'd say use te lever type.
Don't buy one of these:

I did. It was the hardest tool to use. I was able to get one retainer down enough to take off the locks but I broke the tool on the second one.