Safety grounds is a non runner I am afraid.
Look there were 3 type rated pilots on the flight deck of the Turkish 738 that went down on approach to 18R in EHAM. Whilst the guy in the right seat no doubt had very low hours there was a training captain in addition to an f/o on the jump seat and not one of them decided that it was a tad bit strange that the engines had gone to idle, that the captains RA read zero when it should have been reading over a thousand feet a few miles from touchdown and that the nose was continually pitching up on instruction of the AP until it was to late. I can tell you that the accident report will not focus on the poor bloke up to ears in it in the RHS it will be how come two other pilots managed to let him drill them and a bunch of passengers into the ground.
Which airlines are less safe with PTF peeps on them?
You would have more success at citing fatigue inducing factors on safety. Think working for a company that can change your base at will, does not guarantee you an income, long duty days, positioning at your own expense, threatens you with this and that. All on the back of having mounting debts to repay.
There MIGHT be some changes heading our way if the FAA clamps down on the smaller operators following on from the Buffalo crash but don't hold your breath.