Although I have not seen any statistics to back this up, I have heard that you can pass your PPL with fewer hours on a Schweizer. It was designed to be training helicopter, a job which it does admirably. The R22 was designed as cheap personal transport; again, a job it does more than satisfactorily.
However, once you have got your licence, what breed are the nearest helicopters to you? If you have a choice and they are equidistant and you're not totally strapped for cash, the Schweizer can carry 2 passengers (if one of them is thin!!). This may have a bearing on what you plan to do with your licence when you Self-Fly Hire.
The Schweizer handles and feels like a bigger machine, has a fully-articulated rotorhead (which means you can chuck it around the sky), and makes Engine-Off landings a comparative doddle.
Although R22s are the most common training machine, S300s are catching up.
Cheers
Whirlygig
PS - Yes, I AM biased as I learnt on S300C (fuel-injected version - no carb heat) but, as I went through the same decision making process as yourself (Since I also had a choice with Bell 47 and Enstrom 280 thrown in), that was the decision I made.