You hit the nail on the head atlaskid... ASP.net & PHP are going to give you about the same power in terms of web dev, but if you're wanting to distribute you're shiny new projects on the net you'd have to pay excessive amounts for hosting with ASP.net...

In terms of employability... I'd say if you were freelancing, PHP would be the way to go - purely because you can offer your clients great deals on their hosting. However, on the other side of the coin, at the moment there are a crazy amount of jobs available for programmers who use the .net framework - add that to the ease of developing web services... if I was looking to be employed by a big IT company - I'd learn ASP.net everytime.

The other alternative is J2EE - but probably only if you have Java experience; this has the advantage of cheap hosting (it runs easilly on Linux machines/you don't have to have liscences to host with it), with all the power you could ever want... but compared to PHP it's like learning to do complex maths rather than your times tables (in my experience anyway) - even for the simple stuff...

All the best with which ever you choose!

Snow