Well, let me be the fisrt to advice you to get a 361... many others here will as well. I looked at the 390 some time ago and opted for the 361. Better, lighter, and more metal in the right places. I have a 290, the baby brother of the 390 on the same chassis. I used (and stihl use) that saw for several years. The 390 is a good saw, for more occastional use, and under less extreme conditions, and it is $100 cheaper. It will do the job.
That said, the next question is what kind of sawing do you do and how much and for what lengths of time. If you do a lot of sawing for longer periods of time, I would opt for the 361. Less sawing for shorter times, get the 390. If money is not an issue, get the 361. In my opinions, the extra $100 is well spent on the 361, as that is probably the best saw that Stihl has ever designed and produced.
Yes, I know he did not ask about the 361. But I had to tell him about it. I know, I know! But I had to do it! Yes, my precious. I need to tell people about my precious saw. It is an addiction, see? I know that we should be more supportive of other saws, and let people buy the 390, and the Huskies and Jred saws and all, but really. They should at least consider the 361, even if they do not need it. Why? Becasue it is a 361, that's why! What do you mean, I am insane? Well, I was diagnosed with early onset of chainsaw addiction disease of course. And I am in therapy for that, here on AS daily. I am compelled to tell them all about the marvels of the 361. OK, I will try not to do that so muchm, but really, they need to know! They all need to know what it is like to run a 361 in wood and cut like a madman all day, and after it to post more and more about it on AS late at night, see, and it all becomes more and more addicting, see? And the more you use the saw, the more you want to, and ther more you want to the more you post about it, and the more you post about it the more you want to use the saw... and... and... and...