Portable vs. Non-portable for a single computer

...in my experience w/ portable apps - not limited to those from *this* site in the least - I have noticed little or no slowness in starting or operating portable apps. They all act (those that I have run so far, which is at least in the dozens or scores of apps) perfectly well like "installed" apps in terms of speediness and responsiveness.

IOW, while it depends on the individual apps (YMMV - Your Mileage May Vary) - if my experience is any barometer - you needn't be concerned (generally speaking) about slowness and sluggishness of portable apps.

THe conclusion of the matter:
I say, if you can run it portably/find it in a portable format, GO for it, and only be concerned about slowness IF and WHEN you find a particular app that seems sluggish.
Bon appetit!!!...

-Preacher

** - Clarification:
Please note that I have used the term "portable apps", rather than "portableapps" to emphasize that I am talking about apps that are portable generally, rather than apps available from this site specifically.

Such apps may or may not leave traces of themselves behind in registry entries and the like (personally I don't give a rip about such "stealth" performance; I'm only concerned about being able to run an app off a thumbdrive w/o installing an app on someone ELSE's PC...). I don't care. My main emphasis is being able to use APPS that I like anyWHERE I like, w/o restrictions.

The disk size that each portable app takes up is likely to be smaller than the normal installation because PortableApps.com compresses most of the exe's and dll's in an application.

with no major problems. It works and I've not noticed any lack of speed, with exception to a slowdown in Firefox, (there is an issue, I believe with an sqlite file or something like that within Firefox, {search it}. That and the loss of file
associations are the only problems I've encountered. But there is something laying about the forums about an app, that fixes this. I haven't tried it, so I don't know if or how it works. BTW, there is an article or something written about JTH using this method? to refurbish older computers for schools in South America, so I take it that PortableApps.com apps will work where other programs won't. Maybe someone else can confirm this?

There's a lot of things to consider. I want to have all that I see in one post, but I'll be referring to both previous posts.
-Slower startup. Much or little? I think it depends on what do you expect. For me increase 0.2 -> 0.7 s. because splash screen is on for too long is terribly slow.
Of course splash screens can go, then the difference is usually ~0.1s., but it might depend on application - theoretically compression can cause longer startup, but I've never seen it happening.
-Higher memory usage in case that you use several copies of the same program. I guess it might be a problem with things like Chrome, which has each tab in separate process (I might be mistaken here).
-Interferes with MS policy - programs should be placed in a directory where normal user has no write rights. This makes them less secure.
-Smaller size. Depends. Sometimes launcher and belongings add more than compression saves. Some apps are not compressed. Anyway the difference is very low, in your case might be noticeable, but still nothing special.
-Cleanness. Nowadays registry / HDD cleanness has very low significance, even on your machine. However if local programs add some useless shell extensions and / or startup programs, they can be problematic.
-Portability. When you reinstall OS - your apps are already there. When you buy new computer - moving all apps with settings takes just a while.
I'd say - use portable programs, mainly because of the last 2 things. Even if your OS will stay for a few years, then you'll be very happy that your collection of highly customized programs can be just copied. And installing useless crap is rather common.
EDIT: While I've been writing, gmbudwrench posted something new.
-Associations. If you use a file manager other than Explorer, it's not an issue you can easily set it up. Otherwise - there is a program that lets you configure associations and move them around, however I think it's not newbie friendly, so if you're one, you might have problems.

What Preacher said. And, other than file associations, I don't see any reason to install anything other than portable apps. I get upset now if I CAN'T find a portable version of something. I have them on about four different locations, and I can copy newer/updated/newly configured programs from one to another whenever I want. It's the same computer, everywhere.

I wold suggest using PortableApps form here as they are compressed. You can get an App Compressor here and make the apps smaller if you like.

As a result, they are smaller then the installed versions. If you like, you even delete the Help.HTMl and the Other filder, to save some more space.

I use PortableApps for everything I can on my home computer. I will use Development apps, stuff from the forum, and apps I get from PortableFreeware.com and WinPenPack.
I keep a backup of the ones I can't live without.
Only when it is IMPOSSIBLE to get the portable version of an app with that functionality will I install (ack!) something in the traditional way, and when a portable version comes out, I ditch the installed version.

Other than the slow splash screens, I don't see any performance difference with installed vs portable.
The only obvious difference is the lack of file associations and context menus, but I'm using CAFE mod for that so it's easy to get around.