My wife and I have a few OrcaTorch D550, and a D530 along with a few other handheld lights.
My impression/opinion is that a canister light is not really necessary unless it has a significant burn time and that burn time is necessary due to the length of the dives one plans on doing or it is super critical to have extended battery power such as deco dives coupled with wreck/cave penetration.
I can dive for over an hour with the D550/D530 without issue. I typically carry 2 as part of my standard configuration and definitively 2 on a night dive.
If you were asking me, I would recommend saving your money on the D611 or any other canister light unless the type of diving you do dictates the need. For your LOB trip, pick up a spare D550 and perhaps a couple of quality spare 18650 batteries so that you have a backup torch to carry on your night dives and plenty of charged batteries in case you use your torch at all during the day.
The D550 torches are compact, lightweight, and powerful.
I would think that the cord of a canister light is an entanglement hazard and should only be used if the type of diving absolutely requires it....the only thing, in my opinion, a canister light provides on a routine recreational dive is the power cord prevents the light head from falling into the abyss if one was to drop it.
I am not a fan of the soft goodman glove the D550 comes with. I wear my dive computer on a bungee mount on my right forearm/wrist. If I am concerned about dropping my torch I clip the boltsnap to the bungee loop closest to my wrist...the torch then sits comfortably in the crotch of my thumb with a couple of fingers lightly curled on top, kinda like in this picture:
View attachment 620019
But, the D611 does look like a nice canister torch...if that is what you want then go for it.
-Z
@Kriet - All this above.
@Zef covers it all.