The VTC4 is a good battery but only is a 2100mAh.
The VTC5 is a 2600mAh battery but normally way over priced
Easiest way to explain the mAh of a battery is to think of it like a gas
tank on a car.

So the VTC4 holds 2100 gallons of gas and the VTC5 holds 2600 gallons.
Samsung and LG both make 2500mAh
batteries,
but the other day, someone mention the LG 18650HG2
3000mAh 20a
I haven't tried them yet, But with 3000mAh I might have to.
The thing these
batteries all have in common is they don't have the name SONY on them,
so most people don't jack the prices up on them.
I avoid any battery with the word fire in the name, and I won't buy Efest because they exaggerate the battery stats. But besides that I look at the Amps and the mAh.
There's a bunch of good batteries out there, and I rather pay for the extra hundred mAh then a Name.