2 Nanode 1GB vs 1 Linode 2GB

In this particular scenario (e.g. - separating your mail server and web server vs. hosting them on the same server), here are some things to consider:

• Security: If you properly secure your server, this would be less of a potential issue, but if you're concerned about potential server compromises, separating these services would be good.
• Downtime: If one server goes down, the other will likely still be up, and you can spend your time diagnosing the one server/service rather than both email and web services.
• Diagnosing Performance Issues: Similarly, you could diagnose performance issues on these services separately.
• Disk Space: Depending on the volume of email and traffic to your site you receive, if you host both on the same server you're more likely to run out of disk space more quickly. (Consider videos hosted on site, number of emails and size of attachments, etc. This could all add up quickly. With that said, you could still resize your server to a larger plan if they were hosted on the same Linode, but then you'd experience downtime on both services during the resize.)
• Scaling: Separating these services makes scaling and resizing easier. So in a sense, it's not so much a matter of using two Nanodes vs. one 2GB server. Any combination could work, such as one Nanode and one 2GB server, for example.

Thanks @jcardillo for your quick answer, so in matter of hardware there is not different at all, is that?

When you create a new Linode the host is randomly chosen (to help balance overall host loads) so you might end up on an Intel or AMD server, for example. If you were curious which processor the host was using you could run the lscpu command.