Small Engines (Lawn Mowers, etc.): horizontal versus vertical engine, horizontal shafts, vertical shaft

Question
When it comes to delivering power, and a long service life, which would you say is better for a commercial riding mower:  horizontal cranshaft engine or vertical shaft?  When it comes to working on the engine, is one easier to work on than another?
Thanks!

Answer
Hi Ray,

I have had both and can't note a difference.  Horizontal shafts are a little easier to access but in either case, a quality engine hopefully shouldn't require much working on it.  I would look at other aspects of the equipment that it powers.

Best,
Michael