martyn.mahmoud wrote: What's the difference between OpenVZ and Xen?
Is there one better suited towards symfony apps?
In the general case, none at all. You should primarily be looking to get your preferred combo of RAM, disc space and bandwidth. If you have a lightweight site with large traffic, get big bandwidth at the expense of RAM. If you have a very dynamic and interactive site, perhaps with large columnsets, get more RAM and less bandwidth. If you're hosting lots of photos, get lots of disc space, and so on.
Also see if your server location is near your customers - quite a few UK hosts purchase space in US hosts, which tends to be cheaper, but slower for UK users.