10 Speed VS. 11 Speed educate me please ???

11 speed has one more speed than 10 speed......you need it. 

These go to 11.

Whether or not you need it is highly dependent on if you wish you had another gear when riding.

But as for what you need to know...

10 speed rear shifters are not compatible with 11 speed rear derailleurs.  I believe it's possible to get 11 speed shifters to work with 10 speed derailleur.

10 speed chains are slightly different from 11 speed.  

10 speed chainrings are slightly different from 11 speed, but in most cases, you can simply swap out the chainrings instead of buying a whole new crankset.

Some rear hub cassette bodies are only designed to accomodate up to a 10 speed cassette.  I've seen people claim there is a way to convert a cassette body to accomodate 11 speed, but haven't done enough research on it myself.

So in general, in order to convert your bike from 10 speed to 11 speed, you generally will need a new rear derailleur, rear shifter, chain, cassette, chainrings, and possibly a new rear hub.  You may also need a new front derailleur to accomodate the different chain, but I'm not sure on that.  The front is still just 2 positions (small and big ring), but for more precise shifts, I would think the cage would be made specifically for an 11 speed chain.

There is no super huge advantage.  In a couple of years 11-speed will be the standard so all you're doing now is future proofing yourself by going to 11-speed.

I do have 11-speed Dura-ace Di2 on my tri bike.

One of the other advantages is that the shifting is better with closer spaced gears.  Gear changes between cogs that just differ by a single tooth are noticeably crisper than 2 or 3 tooth changes.  With an 11, you can fill in one of those 2 tooth gaps.  People like the smoother shifting, but of course going to 11 will also sell more derailleurs with fans of Spinal Tap.

TW

How I see it: You can only go to 11t on either 10 speed or 11 speed cassettes (yes, there are specialty 10t on smaller hubs). I see no advantage to an additional big cog in the cassette. Unless you're climbing for hours. In that case, ride a road bike.

If you're going from a 10 speed 11t-23t to an 11 speed 11t-23t or even 10 speed 11t-25t to 11 speed 11t-25t, but in most cases, the switch is from 10 speed 11t-23t to 11 speed 11t-25t. Or in reality, many people run 11t-32t or 11t-36t. So the gaps aren't very gradual at all in either 10 or 11 speed.