Coverage Group investment Banking
This is a really tough question to answer because, it depends. It depends on a) the bank's staffing model and b) what level you are at within the bank.
In certain banks, the product bankers are made available as a resource to the industry groups (which I'm assuming you are referring to as 'coverage'). The healthcare group will run the M&A deal, but will call upon the M&A team to consult them on specific technical issues around the transaction. The amount of de facto execution being done at the product level may not be that great. Depending on your level and perspective, that may not be an ideal dynamic for you and you may feel that being on the coverage side will actually get you more execution experience.
Other banks employ the opposite model. Coverage bankers (industry, PE coverage, etc.) originate the deal, but then hand it off to the product guys to execute (M&A, leveraged finance, etc.) Now, as a senior banker, being the coverage banker in this case can be very beneficial. You can focus your efforts on origination which, done right, can be very lucrative.
If you are a junior banker, I think getting as much execution experience as possible will be the best route. If execution sits within the product group, go there. My personal view is that senior bankers get paid more for sourcing new business and, as such, may have better outcomes with more of a coverage focus.