I've seen Blitz3D shots that look better than commercial game engines
Blitz3D is a commercial engine though?
The simple fact of the matter is: you can talk about this engine or that engine until you're blue in the face, but this isn't going to help you complete a game. As Flameduck says, it's not about how powerful the tools are.
And moving from Blitz3D to anything has a learning curve. Learning Blitz3D has a curve too, you've just forgotten about it. If you consider yourself totally proficient with Blitz3D, you should have no issue moving to another engine. There's always the initial bumps when you look at a new language or engine (such as how to initialise a viewport), and this is why I kept turning back to Blitz3D.
But if you get over these with TV3D, you'll realise that the syntax and commandset is just like Blitz3D, but with the added benefits of shaders and fancery trickery. I'm sure the same is true of Ogre etc.