I obtained my residency before I got married. In fact my wife and I were married in the US and my cedula still shows as me being single in the D.R.. So I don't know if being married to a Dominican has anything to do with residency or citizenship. We did own property together in Santo Domingo which maybe helped expedite things. I've been a resident for around ten years and have considered becoming a citizen if only to avoid having to renew my "permanent" residency but don't know which route will result in the least hassle over all.
The sponsored by your wife route would be the best. No need for medicals...etc, less money. I will be doing my oath sometime in February and other than a few hiccups with waiting for police report and dealing with stupid people itès relatively painless.