If you need a 50cc saw get a 346.
Lots of people like that saw. I have it and like it. it's not a so-so saw. It's made a lot of people happy. Even people who aren't drinking the orange Kool-aid (I thought kool-aid was just a stihl thing anyway, right?
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The 346 is pretty light and it is hard to imagine the 550 being much lighter than it in actuality. The 562 ended up being heavier than it was originally stated to be, and I wouldn't be surprised in the 346 did too.
The reviews for the 550xp out of sweden were favorable but not OMFG favorable.
My guess is that the 550 will gain some torque, but you're probably not really after torque in a saw that size.
It will also likely gain pricetag.
It's waiting for uncertainty is what it is. It certainly doesn't sound like it will be a flop, but you might end up waiting quite a while for something that is more or less the same as what you could have now.