2 small servers OR 1 big server?

[foxfox]

Assume budget is limited, you can buy..

a. 2 PowerEdge 860 (1U)
or
b. 1 PowerEdge 2950 (2U)

which would you prefer?

[physics]

I guess it depends on what you want.
IMO, If you want a mirror backup server, load balancing, to run a high traffic site on one and other sites on the other (I guess that'd be poor man's load balancing), or have a separate database server get two 1u servers.
If you want 'power' + ease of use get the 2U.

[foxfox]

but suppose running for a busy site, 2 physcial servers should be more reliable & better performance?

[jatar_k]

as physics said, it depends

without knowing all the ins and outs of a specific situation it is almost impossible for us to answer, there are just too many variables.

you have to know the situation very well to understand the appropriate compromises to make