When considering datcon charging, consider what you'll be logging. Different schools do this differently, but what seems to happen is that what you write down in your logbook (and the instructor signs off on) is what you pay for. So if you fly 1hr in an R44, and pay for 0.9, you log 0.9. I'm not saying anything about whether this is legal or good, just that this is what happens (in my limited experience); I'm happy to be corrected by a flood of schools pointing out that they don't do this.
What this means is that the datacon vs engine thing isn't actually very relevant, except that R44 dual will involve you sitting in the aircraft for slightly longer for the same logged hours than R22 dual will. Or, alternately, all the time you've logged in R44s is actual flying time, whereas your actual R22 flying time will be a bit less than your logged time.
Sloane, are you saying that most people who do PPLs with you in an R22 take 60 hours? How many hours does the average R44 PPL student take? Learning on an R44 has many benefits over learning on an R22, but cost just isn't one of them.
Another possibly relevant point is that if you're planning to buy your own, the insurance will probably be substantially more if you have under 100 hours. Thus doing your PPL in an R22 and converting to an R44 later will get you closer to cheaper insurance for the same money. Just a thought.