jp19sqn is quite right. They are like cars, I suppose, which are all basically for getting from A to B, with different attributes and not able to interchange parts so easily, if at all.
The basic differences between timber and poly can be noted making as sure as it is possible that any converts do not fall into the non-compatibility traps set for them.
Footprint, wall thickness, bee space, roofs, even stands may be different. The fact that, chosen carefully, there is little to modify a great deal, and those changes are relatively easy to do for the average able DIYer. Als that not all new hive components may actually be needed (floors are one area where timber can be substituted without losing any significant benefits).
All in all the benefits certainly outweigh any down-sides - given sound basic choices are made initially.
I chose MB and can use my roofs and floors as well as timber supers, feeders etc. Stands are different if I dont use my timber floors, but all things to think about. No 'compatibility with timber' problem for new starters, if they choose to go the all poly route, but neither necessarily a problem for those who run both - as long as they make the right choices.