The conversions almost always come out better looking. Even starting with a crappy cab I can usually get better results than a scratchbuilt. Yes, there are a few woodworking guru's out there that can produce factory quality cabinets in their garage, but that isn't most people. Also, realize that those amazing looking scratchbuilt cabinets you see in the project announcement threads don't always look so perfect in person (I have seen plenty of scratchbuilt cabs in person).
Even though I'm sure it's all true, I find this paragraph bothersome for a couple of reasons.
For one thing, the original poster was wanting to make a bartop machine, and later changed his plans to a video pinball machine. In neither instance is it helpful to suggest conversion.
But more to the point. . .
Scratch-building cabinets is one of the major activities here on BYOAC, and it sounds like you are dumping on it and the people who do it. It almost sounds like we're all a bunch of dummies who built our own cabinets because we didn't know any better.
My cabinet is my first woodworking project ever. And no, it's not perfect. It has a few minor gaps, and a few bits that should be perfectly parallel and are not. Most of this I think I can conceal. So. . . How perfect does it need to be? I never set out to create a paragon example of fine furniture.
I live in a small town (about 2700 ppl) in a rural area. Even here I think I could have gotten my hands on an old Klax machine for cheap. I looked at it. . . but you know, that wasn't what I wanted. I am building what I wanted. And it has been fun, it's been tremendously satisfying.