One common mistake that most people make, and saw makers thrive on, is buying a saw based on a bar length. That is like buying a car based on the size of the tires it has. You can put 36 inch mudders on a Ford Ranger, but if you don't match the tire size to the engine output, you just have a really tall, underpowered truck. In the chainsaw world, you can have a really long bar that has no power to pull that extra chain through the wood.
You should always buy a saw based on CC's. I prefer a saw in the 50cc range matched with a 16 inch saw. For general carpentry, firewooding and the occasion tree clean up, this is more than enough saw. In fact I own one and use it 5 times more often than my bigger 72cc saw.
As for the comment about keeping a saw sharp, I agree, but would say a sharp saw is more important on a gas powered saw if longevity is what you are after. A dull saw creates a heated chain, and that transfer heat to the bar. keep on using a dull saw and it puts heat down into the crankcase of your saw. Since these are 2 stroke engines that don't get good lubrication down in the crank, you can quickly smoke a crankshaft in very short order. You will also be very exhausted using the thing
Whatever saw you do get, think safety in mind. In Stu's pictures it looks like one has a chain brake, and the other does not. I would get a chain brake. All saws kick back and there is a ton of stories in Maine of people getting biten by a saw. In fact I got a nice gash on my leg from a chainsaw. They are not toys.
Still, stay away from safety chain. All it is, is a dull chainsaw chain. Its safe because it doesn't allow the saw to cut!!
Put on a regular chain, file it often and be wary of the raker height. I file mine pretty low, but I don't allow people to use my saw. It cuts like a son of a gun, but you gotta hold on tight. It kicks.
Now about brands. I know most people on here don't use a saw like I do, or as often, or in felling trees and logs. Still used chainsaws are a dime a dozen. Thats bad if you are buying a new one and trading one in, but if you are looking for a good one, you can get a great deal...at a dealer... and spend just as much as a new lower grade saw from the BORGS. In my opinion, there are only two saw makers. Husky and Stihl. Jonsered is a nice saw but surprisingly it is made by the same company as Husky.
I prefer Stihl. Remember the heat story I was telling you about earlier? Well Husky has a single piston ring. It allows the saw to rev higher in RPMs, but does not cool as well. I have smoked many Husky saws, but never huffed a piston on a Stihl yet. They run slower in rpms, but because they have better compression, you can file your saw to take advantage of their brawn.
Save you money and buy a good used Stihl, that is my opinion. Good, cheap used chainsaws are everywhere!!
