I have an echo cs-620. I would recommend it as that is what I have experience with, and it's not a huge jump in cost between the two, but i'm sure the 590 is great if you want to go with it.
Probably half my posts on this site say roughly this, but again, my newest saw is a Stihl 461. My first SthiI, love it so far. That being said, I'm no lesser a fan of the echo line, if anything, the opposite. (funnily enough, I was going to buy another 620, called around and found one, went to the store and they didn't have actually have it, and decided to get a stihl, and got something bigger, which has come in handy)
I wanted a "pro" saw, love the 461, glad I bought it, but the echo stuff (at least my 620) is great. WAAAAY smaller gap in quality than you would expect for the price. But, the 620 is made in Japan, not sure about the 590.
I'm biased, I have echo everything (blower, string trimmer, power pole saw) but I'm happy with them. If I have one thing against echo, it's not distributing their best products through the big box stores. If someone said to me "I need a chainsaw, recommend me one saw for everything, I would probably say an echo 620, or 590, but most of the big box stores don't have them. Back before I knew anything, I bought a cs-400 at home depot. I don't think there was a $100 bill n price between that and a 590, but they are worlds apart in utility. I don't understand why they push crap through the big box stores, when they have way better products.