I like Lesonal, but you may find that the price difference between the two isn't enough to choose it over Sikkens depending on what discounts he may or may not give you.
Pro-Spray is probably the best "aftermarket" system out there. They have a good system. But Akzo's system of color docs and tools blow them away really. Akzo has a superb camera..probably the best one out there. Their variant deck system is great also. Coverage with Pro-Spray and Lesonal will be about the same. Pro-Spray really lacks just simple color documentation on some areas though. They don't even have a standard swatch of Toyota 040 but list all 100 variants in the computer..lol. I heard for a year that they were releasing thousands more swatches and never saw them. I just made the switch back to Sikkens last week. My jobber had an opportunity to get the whole system in and gave me a good deal so I went with it. Nothing against Pro-Spray though...their old car colors, especially the Mopars, are pretty dang good. I never ran into any issues with the system. Pro-Spray color software is pretty good too. Almost positive whoever deveolped it, developed the Sikkens and Lesonal color software also...a lot of similarities.
I don't know of Pro-Spray would help you, unless it was saving you a little bit of money over the Standox.
Lesonal is going to be a bit thinner than Sikkens..may take a coat more to cover. It requires no binder to mix off the bank so you can just pour a tint, reduce and spray. Sikkens needs 1 binder for basecoat. Pro-Spray has 4 different binders and you'll be using 2 in a mix, and the other two will depend on if it is a metallic or solid color. With lesonal, you can't mix single stage on the bank. Sikkens you can by switching the base binder to single stage binder and can't do metallics. You can with Pro-Spray also by using 2 other binders..they also have different silver metallics for metallic colors if you are spraying single stage metallic. Pro-Spray has a intermix color sealer/engine bay system including on the mix bank also. Sikkens has colorbuild plus for colors for sealer and primer. Lesonal only has a "value" shade system of black, gray, and white. Sikkens has an interior converter for interior parts as does Lesonal. Pro-Spray does not, but they do have codes for interior colors and you can mix as a single stage with flatener.
Just a few things I can think on the top of my head. I used Pro-Spray for a little over a year I think and previously the wanda and Sikkens before that. I'll do my best to help ya answer any questions you have...just shoot.