I understand that people regard the difference between the 6P and the E2e as follows:
E2e - Perfect EDC flashlight (with low output lamp available)
6P - Classic SureFire with a better beam throw (range) compared to the E2e (with high output lamp available) The 6P has the advantage that it can be easily converted into a variety of different models. Here are a few:
KT1 - TurboHead kit
KR2 - NiCad Rechargeable kit
Z49 - Clickie TailCap (many other TailCap options also available)
Z32 - Shock Isolated Bezel
Adding an A19 Body Extender to hold a third SF123A allows you to use the P90/P91 lamps.
The KT2 TurboHead kit (or a variation thereof) is a very useful longer range illumination tool.
I have the opinion that the E2e is specifically for EDC whilst the 6P gives you more options then you can shake a stick at.
Personally, I'd get the E2e-HA.
To use the P61 high output lamp for two cell SureFires, I'd pick the M2 or G2Z over the 6P.
Al