The client's account is something that should be used for the actual listing being edited by that account. As Linda said it is best to do edits for that business in the dash. And if it affects the business like Colan said to use the troubleshooter.
What it sounds like you are describing here is making reports/edits of existing businesses on the map that aren't clients of yours for which there is an account or duplicates of businesses you are working with. It is a good idea to build trust in one account for the other GMM users/reviewers to know and recognize. The type of edits you make, unless you do general editing, will be obvious that you're an SEO so I wouldn't worry about editing all over, as many people in your line of work (or not) do it all ready.
What is important is to never use multiple accounts to accomplish one task, ie making and edit in one account and approving/reviewing in another. That's a BIG no-no and can result in all the accounts being shut-down. Also, making quality edits is key. You don't want to rack up many bad edits in MapMaker (what edit business details uses for processing direct action edits). When using Edit Business Details it is possible to not do the edit in MapMaker but you have to use the upper selections and not touch the lower fields which relate to the feature.
If you feel comfortable with using your personal account to make general housekeeping edits then use that. If you don't want to mix work with personal then use one just for work and personal for everything else. Just don't overlapp the acitivity in those accounts and Google will stay happy. Additionally you shouldn't be using MapMaker, etc for edits which you can accomplish in the Dashboard as it is a trusted source of data for that feature and it is the best way to give feedback to Google about that feature.
Think of multiple accounts (including client accounts) as circles of trust. They should only be used for what's covered by the circle, ie client dashboard/account is for that feature which that account was created for. It isn't for marking your favorite vacation spot for. You could do it but it detracts from the effectiveness of all your accounts (yes Google collates access across accounts behind the scenes when it feels it nessecary). So if you can't indicate duplicates in the dashboard I'd use your normal account for reporting duplicates and other tangentally related issues. But if its for the actual business (name, address, etc) you should be using the dashboard because to otherwise would circumvent the trusted feedback to Google.
I hope I have described this adequately. Please let me know if there is something that doesn't make sense or needs more clarification.
