I have AMD Mobility Radeon HD 5730 and use a external monitor instead original. I always have problem after updates with good working with this solutions. Often i must reinstall system because i have to black screen or something light that. Now in 15.10 works, should i upgrade ? I read some times ago amd not support 16.04, now it's better ?
It's not that AMD isn't supported in 16.04, it's just that there are no proprietary drivers for AMD in 16.04. This basically means almost all games are out of the question, but most other things, including videos, should be fine.
If 15.10 is working for you, you have a difficult decision.
15.10 has reached its end-of-life date today, meaning we at Ask Ubuntu will no longer support you if you have any problems. You will also not get any security updates, as the default repositories for EOL releases are frozen.
16.04 is supported, and will be supported until 2021, as it is an LTS (long-term support) release. These happen every two years (12.04 in 2012, 14.04 in 2014, 16.04 in 2016, 18.04 in 2018, etc) and are supported for 5 years after release. However, 16.04 loses any performance you may need from your AMD graphics.
You can either stay with 15.10, with everything working how you want, without any updates or support from us, or you can upgrade to 16.04, which is supported and will receive updates until 2021, risking the performance loss.
If you do stay in 15.10, you can always visit [unix.se] for help, but chances are they will suggest you upgrade to 16.04 to solve any problems.
I can't tell you which to choose, but I can recommend that you take the performance loss and upgrade to 16.04 for the support. And who knows? Maybe a great AMD driver will be released soon.