I'll add this on the end of the other - the orbies are great in the 3.7v range and take ages to drop off, so the basic idea is you drop a wrap from your coil so that as the battery drains, you are in that "flat" area of the battery discharge curve for longer. I use a 0.7Ω coil and can just about squeeze a working day from them.
But vtc5's if it were my cash. On the other side of the coin - i use a mech, so my desk has on it MNKEs, Samsungs and about 11 orbies, from PDs to SX30s.
They also ship free and since i only change them at about 3.6v, the performance below that is irrelevant to me, because that is the point at which they feel weak.
T