The main thing with rawhide is you want to go with good quality sun dried rawhide that has not been bleached (as in not the white stuff that doesn't smell) Bleached rawhide is not so great for the obvious reasons, cheaper brown rawhide is often cured with arsenic (which of course is supposedly safe at specific levels) I don't give rawhide too often and when I do it's hard pressed sun dried brown rawhide.
And never give a dog rawhide 'flips' as then can swallow them all goobered up and are a major choking hazzard. Another thing to avoid is rawhide with knots in the end, some dogs chew off the knot and swallow it whole.
Tennis balls, my ball crazy dogs teeth are fine (and the one who's aren't fine is a rock chewer so I tend to blame the rocks:LOL-she's only got 1/2 a K-9 left, we call her gumby) I will warn you though, I had an old shepherd who swallowed a tennis ball whole once--it was a very costly 30 cent ball!! He was playing flyball and he had a habit of carrying more than one ball (his record was 7) and he was coming back over the jumps, saw a ball in the other lane, swallowed the ball he'd caught at the box and grabbed the second ball off the floor. Few dogs are that insane though :LOL