what are the pros and cons. front or rear hub work better than the other. ease of instalation repair, cost etc. seriously concidering converting one of my many bikes to electric for them lazy days when i dont want to pedal to work.

I like the look of rear hub but can't find anything actually wrong with a front hub. Too much motor might slip on steep grades but stand on peddles and lean forward.

Front hub very easy to install compared to rear hub dealing with cogs and stuff.

Easy to get too much weight over rear wheel too

From my experience, and these are generalizations, there are always exceptions and some brands have offerings that others don't - BionX having 9 speed freewheels, or eZee having front disk brakes for instance.

Front hub:
+Typically cheaper
+Easier to install
+Easier to revert back (which is nicer for one-bike sorts, who might want to do weekend rides and the like)
+Retain original choice of drivetrain (you can keep 9-speeds, IGH, etc)
+Repairing tube/tire damage is easier
-Less traction than rear wheel
-Many suspension/aluminum forks too fragile/unsuited for long term use and will fail

Rear hub:
+More robust (no worries about head tube/fork damage, the rear dropouts are made for torque)
+Easily meshes with suspension
-Limited drivetrain options (most models are only compatible with 8 speeds or less - freewheel only)
-Repairing flats can be more difficult
-Slightly more expensive (little difference if your current drivetrain is compatible, more if you need to change parts over)
-Installation and reverting can mean work - although not a serious amount, it is more than front wheel

With both motors being the same make and model, performance between front and rear is pretty much the same. My primary deciding factors would be suspension compatibility and whether or not the motor was being used for high demand/power applications.

I'm running both a front and rear hub currently and have built up four front hub bikes. My rear hub is my latest build.

Front hubs only have a problem with powerful units accelerating through turns. They tend to push the bike starboard (left) and it is possible to lose control. My 500W Wilderness Energy had a real issue with that. The 400W brushed hub on my beater is unphazed and offers excellent control in the corners, but then again sometimes it's hard to tell if it's on.

I've just finished my latest build with a Crystalyte 500W 36V rear hub. There is a lot of weight on the rear end and I'll have to get back to you about how that can effect (or affect) performance. Right now I'm just putting a Specialized Armadillo tire on the back because I fear rear flats more than anything.

I have a front e-hub from WE (BL-36). I like how the weight from the front wheel and the weight from the battery pack in the back of the bike, balances out the bike nicely. Also, having a front e-hub combined with rear wheel pedaling gives me an all wheel (AWD) driving experience. When climbing hills, seems to me front wheel drives might have a better pulling power (like a car).