I have 4.1 and I want 5.5. Upgrade o fresh install?

Hello!

The question is simple. I have a cluster with 2 ESXi 4.1 and I want to move to 5.5 version. It's a good idea upgrade directly? Or better do a fresh install of 5.5 version directly?

In case I could upgrade, is better doing with Update Manager, o manually with USB boot image?

Thanks!