asp.net - WCF vs ASPX webmethods vs ASMX webmethods -

the intent create set of web services people can reuse. these services interact backend db creating, retreiving , processing data.

we want expose services people can use create data mashups , other applications.

end users webpages can within our domain or outside our domain. pages outside domain plan release widgets configured retreive , display data.

one requirement - application should extremely scalable in terms of number of users can handle.

our code base .net , looking @ aspx webmethods (or ashx), asmx webmethods , wcf (starting read on wcf).

in terms of security/access found maintaining sessionid, memberships doable in three. wcf seems bit complicated setup. not see value of asmx when can done using webmethod in aspx (with little tweaking).

also, assuming asp.net mvc2 might able clean urls these webmethods.

questions

which 1 effective in terms of performance , scalability? reason why should choose wcf or asmx?

thank taking time read through post , apologies naive questions since new .net.

edit kind of understand wcf way go. understand evolution of technologies if can throw light on why aspx webmethod different asmx when similar things (apart discovery) can accomplished both. aspx webmethods can made return data in other formats (plaintext, json). also, seems can build restful services using ashx. apologies again naive questions.

you should use wcf developing webservices in .net. wcf highly configurable many options security, transport protocols, serialization, extensions etc. raw performance higher. wcf being actively developed , many new features being added in version 3.5 , 4. there variations wcf data services , wcf ria services. wcf 4.0 has better rest , json support can directly use in asp.net / jquery.