I have tha Patima housing for my G11 and use my "old" Inon D-2000 Strobe with it.
Pros of the Patima housing:
- VERY sturdy (usual comments: built like a tank)
- very good quality and production
- WA and zoom port included
- WA port accept all 67mm wet lenses and filters
Cons of tha Patima Housing:
- very heavy and negative boyancy
- use of internal strobe not possible
- expensive
Pros of the Ikelite housing:
- Good and tested quality
- internal strobe may be used ( but only in telemacro)
- macro, "wet dome port" wet lenses and colour correcting filters
- free choice of internal, external slave or external corded strobe
- Canon eTTL conversion circuit included for true eTTL using a Ikelite DS series strobe
- relatively leight weight
- reasonable price
Cons of the Ikelite housing:
- Effective use of internal strobe is limited to macro photography at a distance of less than 2 feet (0.6m).
- WD-4 "dome port" is a wet dome port and may be tricky to use
The Patima or FIX aluminium housing are almost professional housings with a respective "professional" price. The best choice for a G11 housing for "normal" use is the Ikelite.
I agree with Nemrod about the Inon D-2000 strobes, relatively small, powerful, sturdy and to use with various settings (full manual, automatic and s-ttl)
If you need maximum power the Z-240 have slightly more power, if size, weight and price is a concern, the sweet, little S-2000 may be perfect with a slightly lower (unverified) output.
If you would like to take advantage of the eTTL using the Ikelite housing, the Ikelite DS-161/161/200 are very sturdy, but bulky strobes.
Chris
P.S.
Is the price difference worth it? Yes, but only if you need a rugged aluminium housing.
I am dive instructor and need a super sturdy housing to have with me every day,
A weekend and holiday diver may take more care of his gear and so the Ikelite or OEM
housing may be fine too.