I had the 300 (not sure which version, looks like whatever is currently listed on amazon) and then got the 365. The main difference is the batteries really. The 300 uses a flat wide watch like battery (don't know the exact name, don't have it in front of me) while the 365 uses a regular AAA battery. The 300 batteries run out really quickly and the AAA model is much more desirable (I use eneloop rechargeable a in mine). I sold the 300 and am very happy with the 365.
