I don't really understand hyour questions. I have been working for the last couple of years with an ODM in Taiwan that uses ProE, so I have lots of experience importing their files, making modifications in Solidworks, and then exporting back to ProE. I have had files where I had to spend more time fixing the files so that I could work on them than I did doing the actual work, but it has, in general, worked reasonably well.
I'm afraid I can't comment on how ProE compares to SW, since I haven't been running both.
In the next couple of months I probably will be able to comment about how Creo Parametric compares to SW, as we are going to start using Creo. It doesn't look like I will get much design time in though, so I'm not sure how much I will learn.
I use both SW and Proe WildFire4 and CREO in my job. You can work much faster conceptually in SW than you can in Proe (regardless of ProE version.) After being product manager for SW for 9 and 1/2 years and just getting my hands back on Pro - astounding how little it has changed! Oh, it might have changed as far as some window dressing (Creo) but it is still a crappy interface. It does have a robust modeling kernel, but there is nothing it can do better from a geometric creation standpoint (including surfacing) than SW. With Replace sketch entity, Style Spline, Power Surfacing add-in and Conic fillets, SW pretty much bests Pro in the consumer product work that we do here. Proe does still do some things better but they are not important enough when you consider just how much more productive you can be with SW.
Now I need to get back to my WF4 project.... pray for me!