Since I own, or have owned and used just about every saw in the current Echo line-up, here's my 2 cents worth.
The reed valve top handle saws, 300's, 301's, etc and WAY, WAY underpowered, and don't have much grunt to go with there poor power production. They run fine, and hack away at small limbs just fine, but they are not overly powerful in any rpm range. I could start on a 10" log with one, and have another cup of coffee and a donut before they'd get thru it!
The CS-360T is a completely different deal, PLENTY of power over a broad rpm range, grunts along fine, but really likes running WAY up in the rpm range. It's happiest right up near the rev limiter (apprx 14,500rpm's), and easily rivals the Husky and Stihl top handle offerings at less than half the price.
The CS-440 was OK, good upper mid-range power curve, well suited to a 16" bar, maxxed out with an 18" bar. Even though it's just a tad smaller than the CS-510, it's not nearly as powerful anyplace. I will say that we left this unit stone stock, and have mildly modded the 510's, but they still ran quite a bit better everyplace before we touched them.
The CS-510's are EXCELLENT. Broad power curves, run equally as well at every level compared to a Husky 55. The 55 only shines a bit more right up at the top of the rpm range, but doesn't have a power curve quite as smooth as the 510, or pull as well when it comes out of it's "sweet-spot" in the rpm range.
The CS-670 was somewhat of a disappointment to me. Decent power everyplace, but the Husqvarna 268XP killed it at every level. I sold that saw and have replaced it with a CS-6700, which we are going to modify and test with porting, muffler mods, less quench area, etc, to see if the power can be improved some?
The CS-800 was a big, heavy, grunt saw. Actually the most disappointing off all the Echo saws we obtained/tested. It did NOT use the automotive type spin on air filter, and had a goofy rubber plug to remove to access the mixture screws. It was simply OK with a 24" bar, but wouldn't even cut as well anyplace as our nearly 30 year old Husky 480CD. The 800 also comsumed a LOT of fuel. It reminded me of the old 038 we dumped on E-Bay a while back, make a couple dozen cuts and you were putting a quart of gas in it, and no "bling" while making the cuts, just a flat/boring power curve.
The little CS-370 is becoming one of my favorite little saws. I ported the intake elbow and muffler, it's quite a runner for 36cc. Not much of a high rpm saw, but excellent mid and upper mid-range characteristics, with PLENTY of grunt to go with it. I had it in the woodpile last night cross cutting big hunks of dry oak and beech, without a grumble with bar completely buried in them. Exactly the oppositie results I was anticipating. I figured the engineers would give the little saws sparkling top end power, for fast limbing capabilities, not broad power with plenty of grunt for larger cutting jobs.
In any case, I am still very partial to my Husqvarna saws, and seldom venture very far without my 262XP or 268XP. I still take the CS-510 to every outing, along with the 55 Husky, as they are plenty of saw for most of the tops we cut.
What I love most about our entire line of Echo power equipment, which includes 2 leaf blowers, garden tiller, string trimmer and several saws, DEAD SOLID reliability in every area. At most 3 pulls to start any of them, doesn't matter how long they sit. NEVER bought a single replacment part for any of them, tough as nails and well suited for any of the tasks they were built for.
IF I were starting out in a tree service business, I wouldn't hesitate for one second to include quite a few of the smaller Echo saws in my line-up, and take the money saved to pick up a couple of Husqvarna 372XP's or maybe even a larger Stihl saw or two.
Folks, I obtained our CS-360T on E-Bay new for $170, the CS-370 for $148, the CS-6700 used for $46 (needs P/C). My total investment in three dead solid reliable saws will be less than the cost of ONE Stihl 200T! The reality of the situation is that I have a nice line-up of saws at a very low investment. I started out just trying to find out if these units were as bad as many folks say they are? I'm finding out that Echo makes some excellent quality saws, they just may not "bling" quite as well as the lengendary stuff, and sparkle as much, but they sure do fine getting the work done!.......Cliff