They are different.
- 42 (either 300 or 500) flys a lot nicer and has very stable handling characteristics particulary during landing. Some models also have an extra stage of flap.
- 72 by its stretched nature is more difficult to fly and less stable especially during landing and crosswind conditions.
All that said it's a moot point, Yeti only operates 72-500 so theres no switching between types in their airline.
@ZFT I don't really see the relevance of differentiating between PEC and Non-PEC models (300 -500/600) of the ATRs. It bears no interest to the topic, moreover it comes down to pilot preference. Some pilots prefer the Non-PEC models because they aren't as slippery but apart from having to set the props yourself they are no different