Do you ever edit dialogue on cans?
What if your speakers are sub-pro, is it better to edit the dialogue on a decent pair of headphones?
I've done a lot of dialogue editing on headphones. Bear in mind though that this was game VO editing, which is quite a different process from being a dialogue editor on film, as far as I'm aware. With games you tend to just worry about single assets - if they're topped/tailed correctly, the file naming conventions, if there's no horrible clicks or other stuff like that in the asset, if there's perhaps some issues with the actor's performance of that particular line.
So in that situation, editing on cans was always fine - and indeed often easier to spot little issues like clicks. The flipside is that you can start worrying about things that in the larger scale of the project don't really matter, and that slows you down. When you have 45.000 lines of dialogue to edit, you don't want to slow down, as you can imagine. So bottom line has been for me, on projects like this, to be able to get a feel of what is an issue and what you can let slip, as listening to isolated dialogue on headphones reveals a lot of tiny things that will pretty much go by unnoticed for the player or audience.
The one thing cans can't help you do is check phase, which CAN be done on even the worst set of stereo speakers. So, in my opinion, I think you may be better off doing the bulk of your editing with the headphones and checking it against your speakers after you're comfortable with it there, check it for phasing issues in the speakers.
As soon as you can, invest in a set of monitors. No matter how cheap they are, they'll be better for editing than the nicest set of "audiophile grade" hi-fi speakers.
I´ve recently edited dialog, fx and music of a 90 min documentary using a pair of headphones. At first it was a portability issue, but then I found out that they gave me a greater level of detail even in quiet passages and a response more dynamic than my pair of NS10m or some bigger Genelec. This cans were Grado SR325is, they are the "best" of the lower range -in the same price range of most common pro cans- and I´d recommend them to anyone.
I've done a few dialogue edits in my headphones. Like others have said, it's great for cleaning up clicks and perfecting transitions. It is crucial to be able to reference what you've done through monitors though. I like to do my clean up with my headphones for a scene, then have a listen through the monitors. After your ears get accustomed to hearing pops and clicks in headphones, you won't let em sneak by you in monitors.
I love to have my headphones around all the time. I have the Beyer Dynamic DT-880. Translate pretty well. Best headphones I've ever had.
I mainly work on projects for film or tv and i avoid cans like the plague. As we're always mixing for loudspeakers (To the veterans: do you guys ever take headphones into account when you mix?), headphones give a very inaccurate representation. I see what you're getting at, using them as a magnifying glass to find clicks; but i think this could lead you to agonise over things that aren't even audible through speakers. Also, if you're trying to fit in alts and whatnot, they could lead you to think something doesn't match when it does or vice versa.
If you have a nice, quiet room and a decent set of monitors (although sometimes the ideal conditions are hard to get hold of), i don't think cans should be used.
Edit: Just reread your question; if your speakers aren't amazing, then i'd do a pass with each to get a better perspective on how it's sounding.
My company tracks a good amount of audio books and headphones are standard for this type of session. You will catch little things that need to be picked up in the cans that you might not in the monitors. This type of workflow was actually pressed on me from the producers that produce high profile audio books daily. Whatever you are working on, if your end user will be listening on headphones, you should be doing a good amount of it yourself.
Have I edited with cans? Sure. Mixed? Hell no.
It's usually due to unideal circustances. Like, because it's 2am and I don't want to bother anyone. But yeah, it can be done. Just know your cans, know how they translate, and compensate for what you're missing.
Of course if it came down to an awesome set of cans or a mediocre set of speakers, I'd choose the speakers.
I think it's important to cross reference, constantly. If you've got a setup and playback system you are comfortable with and can trust, i.e headphones and decent reference monitors, this process shouldn't slow you down and with more experience you get to know what particular device is better suited to the detail or the abstract of what you are editing. For me, headphones are great, mdr 7506, every tiny detail can be analysed.