RE: Is a bigger plane better to train with?
True enough. "Biggerness" is more felt in weight and wing loading than wingspan alone.
Remember for your work bench consideration: 90% of the building for a wing with seperated spars is at 1/2 the wing's width. Only the last little connection and sheeting phase (where one side is blocked up and can be over a chair or on the floor anyway) is full width building. Whan sanding and covering it doesn't matter if half is out in space beside the table.
Transportation and storage is more often the limiting factor.