[Will]

If you want all your forums to link up, I'm almost 100% sure they'll need to be on the same database, so you'd need the same forum software.

1and1 are fine if:
- You don't mind limitations of your forum size.
- You don't mind limitations on how many emails you can send.
- You don't mind limitations on how many databases you can have, and how you are allowed to use them.
- You don't mind limitations on how many database users you want.
-etc.

Basically, if you don't mind limitations on absolutely everything, 1and1 are great.

As far as I know ASO have no rules on chat, they have no limits on anything apart from the bandwidth and server space. There's probably better out there, but after using 5 different hosts, I haven't found one.