What will you be using it for?
The MS170 is a fine saw for the average city dwelling homeowner doing yard cleanup occasionally, or for light limbing, but it would not be my choice if cutting wood for heating with all winter. Is it better than an inexpensive Homelite? Absolutely!
For anything heavier I would recommend a MS260 or larger. More tons of wood are likely cut each year by folks with MS290's than any other saw. They are popular with many because they are not so big that they are unwieldy, yet are capable of doing most things that the average suburban or rural homeowner needs done in most cases.
If you intend to be felling trees and cutting a lot of wood, like to heat with, I would suggest not only a larger saw, but probably two saws. A big one for big wood, felling, and heavy work, and a smaller one for limbing and most bucking.
I heat with wood, and I have three saws that I regularly use. I've got an old 018 for limbing and light work (that I want to replace soon with a 260 or 290), an MS391 for felling smaller trees (up to about 16") and most bucking, and an old 066 Magnum for all the bigger stuff. This gives me saws of three distinct displacement classes. A 30+cc, a 60+cc and a 90+cc, running bar lengths from 14"-36".
Think about what you want it to do in terms of the size wood it will have to cut, and the frequency that it will be used, then buy accordingly.
Also very important, leave room in your budget for safety gear. Eye protection, gloves, boots, and chainsaw chaps are a minimum. A chainsaw can hurt you badly and fast. Good safety gear doesn't replace common sense, foresight, and being careful, but it will save you a lot of pain and a trip to the ER if you should happen to have something go wrong or just an "oops" moment. Check out YouTube or Google images of "chainsaw accidents" to see what happens and get a good scare about what happens w/o good safety gear.
Keep your chain sharp, let the saw do the work, and wear your gear! Safety is paramount!
Good luck!!
(Been heating with wood for over 30 years, so we need a saw with some guts. Stihl's have always been great saws.)
