obviously both you can trust, but being that its your buddy I would choose the one that will throw you a 100 when he deposits 500 or something since they both will payout and are safe (I am sure)
5 dimes has better reduced juice.. heritage has better contest freeplays n things I believe.. 5dimes seems to offer a bit more things to bet (but I dont do most exotics so I have no real number comparison there)
If he is looking for a big bonus, I wouldnt choose either of those places though to be honest.. 100% deals never come from them of course.
-murph