Go with the porter cable, if you can save some moeny and wait get a better one like a excalibur, don't get those cheap ones like the HF or craftsman ryboi and the likes, they won't hold up they may last a few weeks a few months or years. I had a craftsman when I first started was a great starter saw but in a year I worn out to junk, I now have a excalibur 16 inch and love it, smooth and cuts good. In the end I should have waited and got the ex from the begining.
Can google the difference in the arms, the C arms you talking about are like the cheap saws, craftsman ryboi, you have two arms that move and up and down, this motion does have some flaws, it has a sawing motion, meaning as the blade moves up and down it does slighty make the blade move front to back, this gives a bit less control and not real smooth, the higher end saws Excalibur and dewalt have the parallel arms, this setup gives the blade a better up down motion with very slight at all front to back movement, this type of saw gives better smooth control with the C arms that tend to want to so to say push the wood or make it jerk front to back, there is a article i read that expained the types of saws, this is the best I can explain it.