x86 VS x64 Portable Apps on a x64 Machine

[guinness]

Obviously the majority of 32bit Portable Apps can run on a 64bit machine, but if there is a 64bit application available, what is best to use the 32bit or 64bit? Or should the user re-download their favourite applications that have a 64bit variation.

e.g. Defraggler has both 32bit and 64bit available, the 32bit works perfectly so what does the 64bit do that the 32bit doesn't. (Probably faster loading, but anything else?) I know the 64bit is included in the .ZIP, but this applies to other Portable Software.

Note: Not much has been brought up on the subject of x64 so I wanted to ask a standard question, that you find on forums about Installed Apps.

[joby_toss]

Off topic: man, I'd like so much to get my hands on a 64bit windows version!
If I'd have one, I'd use only 64bit apps if available. Why? What is the point of going 64bit then?

[m^(2)]

There are many points for and against x64. I have XP x64 and use x64 apps only when I need to...and then always have 2 versions with a launcher that runs the proper one. That's because few if any would benefit from it (I don't have 3+GB of RAM. Actually 1 GB.) and I highly benefit from 32 bit compatibility - several times I moved parts of my toolset to portable devices and used on 32bit systems. If I used x64 apps, this would require redownloading.

My take is: If you're sure you'll never move your apps to 32 bit system, then use x64. If you run some code that has optimized x64 build and really runs significantly faster, use x64. If you have 3+GB of RAM and want single application to use large part of it (i.e. 7zip with large dictionaries), use x64. If 32 bit version doesn't work properly on x64 system, use x64.
Otherwise use x86.