Multiple Characters or One?

I have run into a bit of a conundrum in my recent return to Diablo III.  Should I focus on one level 70 character or should I just mess around on several?  I have no intention of trying to earn any special place on a leaderboard and I just mostly play for fun.  My crusader has come along nicely and seems decently geared.  I also have a level 70 monk who is really fun, but could use some shiny new legendaries.  So how do you roll?  Do you focus on one set class or do you choose from a set?

I really like my monk.

If I roll one toon:

1.) Better chance of gearing up a character and increasing the difficulty level resulting in better loot.

2.) More practice with one specific class.  Gain a more thorough understanding about class abilities and how to most effectively use them.

If I roll with multiple toons:

1.) Grinding becomes less stale.  Simply switching classes makes things feel different.

2.) More experience with different classes.  I'm not expecting to play multi-player anytime soon, but understanding other classes is good.  I've always enjoyed learning every class in games.

3.) Spread the wealth--gear up multiple toons with drops.  Choose the best for each situation.

Or, the random thrid option is to look into the whole seasonal play.  I haven't tried to make a seasonal hero yet, but as a fan of levelling I could see this as a valid option.  As a casual player I wouldn't expect to get much out of it--I won't be on any leaderboards.

These are my Diablo dilemmas.  /sigh.