For my site it is pretty common for SEOmoz to find things before WMT and for the items to disappear from my dashboard a lot sooner than in my WMT account.
I am always looking at both sources to figure out the issues that need to be fixed. Generally I find that SEOmoz is more comprehensive in finding duplicate page titles on my site provided that they are internally linked and within my 10,000 page crawling limit. WMT will often identify pages that I forgot even existed or that are orphaned.
As far as SEOmoz showing pages that have duplicate titles that aren't duplicates I have only seen that a couple of times and it fixed itself with the next crawl. I attributed it to a glitch and haven't seen it recently.