As a flight instructor I like the 300C for flight instruction. Taught a little in Jetrangers and 500's but find the 300C a tough aircraft. When teaching touch down auto's it can be dropped from about 5 feet and not get damaged. Nevr flew a R-22 so can't comment on it. The flight school I worked for as a part time instructor recently went out of buisness as the insurance went up some 45 %.
The r-22 appears to be getting the job done as a primary trainer and is around $30 cheaper to rent than the 300C. Bottom line, if you develope a good foundation you will beable to fly any helicopter safely.
SKYCOP9