Currently I am getting next day transfers with my 3rd party merchant, authorize.net reseller. That's really the only big turn on for me versus going direct. I suggest you give a few banks a call and see what they can do for you.
A 3rd party merchant account is a sponsored account which is hold by the processor and where you transactions basicly are mixed with other merchants, you will also use the descriptor hte processor choice and can't get your own.
With a direct merchant account / MID you will have your merchant account directly with the bank, have a own descriptor and no one else will use the account, often this is cheaper, faster payouts an safe you to be burned by any processor.
A lot of excellent points have been made here on this. I'd add another point - in my opinion, if you can't obtain a direct merchant account due to your geographic location, sometimes a 3rd party account can be the only option.
However, that said... if you ARE able to be approved for a direct merchant account I would always recommend going in that direction UNLESS you process so few transactions that even a $10 or $20 monthly fee is going to be an issue for you. If that is the case, consider using PayPal - it is probably the most stable of the 3rd party options available.
For all other businesses, a direct account is going to give you much more control over your billings and customer data and provide a much more cost effective and flexible solution.
In the last 15 years I've seen a long list of 3rd party processors come and go and when they go - they usually leave with a pile of other people's money with them. Just look for threads about "PaySystems" for one prominent example from a few years back.
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