Three mediums is a great way to go! They are not only lighter to lift, but all of your equipment will be uniform!
Honey production, swarm prevention, and colony build up should all be the same as using deeps, the bees don't know the difference between three mediums and two deeps, it's all usable space to them! If you're making your own splits, then you have no worries there either, it'll all be your equipment.
Brian brings up a good point about nucs, if you ever want to buy a nuc they will come on deep equipment but there are ways around this also. If you had one or two deep boxes to put on the bottom, and stacked your mediums on top of them, once the bees move up out of that deep, you can just rotate it out of the hive.
Good choice for light weight and uniformity! Good luck! :D