Ok, after reading around this is what I have found...

If I use a 1700kv setup
5s 5800mah weight 776g
5s 5000mah weight 704g
If I use a 1900-2200kv setup
4's 5800mah weight 568g

Now the weight difference of 208g from the 4's 5800 to the 5's 5800 seems alot to me.
If my setup is geared for 38-40mph on any of the combos which would give me the longest runtime?