A lot of times my clients ask me which plateform would be better for their website PHP or asp.net. Today I will try and explain the differences in these two:

1).Performance:  Performance wise asp.net is faster then php.

(source http://www.wrensoft.com/zoom/benchmarks.html)

2).Cost Effecient: Here PHP scores over asp.net as php is open source and readily available over internet for free.

3).Support & Third party Tools: Plenty of third party tools and support available over internet for asp.net

(Though they may be expensive)

4).Ease of programming: From a programmer point of view it is much easier and faster to develop applications using visual studio due to better tools and controls available as compared to PHP.

5).Plateform Independence: Micsosoft's asp.net is supported to run only on windows. Though a project named Mono has been developed but still it is in early stages. Whereas PHP can be run on linux as well as windows.

At last choice between both depend apoun the company and its circumstances. If a company has resources then it should go with asp.net and if it has a relatively smaller resource pool then it should be better to choose PHP.