A shell is a bit more expensive then a real shell. If you just plan to host an eggdrop, what is the disadvantage of a webinterface compared to a ssh account? To you suggest not to use a webinterface?
A web interface can't possibly give you as much access to utilities and compilers as a real shell. At least, I've never seen one that did. You probably wouldn't have access to running things in the background with 'screen' either, which would definitely hinder running an eggdrop.
totally agree if it is just for eggdrops, CLI or console for ssh2 is a lot mroe flexible and useful for extras like maybe a webhost or forum addons to your account then yes plesk or cpanel or good old usermin is nice to use.