after many many decades of cutting wood I find there are many truths when it comes to chainsaws.... you know those little 40 - 80 cc engined machines we want to run at 13,000 - 15,000 rpm.... often without proper warm up, often with gas that has sat for much longer than it should, often after sitting for many many months with little TLC....
My own Rules that I live by:
1) buy the best saw you can afford. Yes I have owned entry level saws such as Poulan that have worked super and lasted an unbelievable amount of time but my experience is somewhat rare. You get what you pay for.
2) Maintenance is not the same as fixing a saw that doesn't run well. So I change plugs frequently as getting timing clean on something that sparks
200 - 250 time per second !!! is pretty special, fresh fuel only (I will dump fuel before I use old fuel), clean air filters and fuel filters regularly, and replace the gas lines/fuel pickup line/primer bulb EVERY YEAR. I am amazed how many people come to me with saws not running well that have never changed the fuel pickup line even once when many brands want them changed annually.
and my saws almost never let me down.
Brands... I have strong preference for Stihl as my local dealer treats me well and keeps huge inventory of spare parts but there are many good brands out there..... I even had a Poulan Pro that I probably cut 100+ cords of 18" rounds with only because it was given to me as a gift. It finally met its final resting place as I couldn't get an OEM replacement ignition module for it.
Most fondly remembered was Pioneer P65 but that brand disappeared almost 40 years ago when swalled up by Husqvarna.
My favourite all round saw today is a Stihl 261c which is a commercial saw with electronic engine management. Great all around saw for a guy who cuts mostly Jack Pine as rarely get anything greater than 16" diameters. Jury on my end still out whether electronic engine management will give me 200+ cords of of 18" rounds but so far so good.

on the western edge of a chainsaw is clearly my happy place. My wife knows she comes second when its saw time.