Yes, obviously Classic Windows will be faster simply because there are less calculations to do. That’s also why it depends on the system. On fast systems, the performance improvement will be much less than on slower ones. It is the CPU that plays the role here since in XP, the theme is not done in the video card (yes, you’ll notice Explorer is slower without proper drivers, but you won’t see it faster if you have a better card because the acceleration is basic, eg no 3D stuff and the overlay surface is not used for windows).
I personally always use Classic Windows, even in Windows 7. It definitely feels snappier and more responsive, but on a more objective note, there are other issues with themes.
One issue with most themes other than the ones that come with Windows (Luna in XP), is that most themes tend to be designed without an eye for detail or usability. Specifically, I find it incredibly annoying when I swish the cursor into the top-right corner of the screen to click the ☒ button to close a window and find it does not work because the theme has offset the button or the window has a rounded corner even in maximized mode. I then have to move the cursor more carefully (and slower) to make sure that I hit the button instead of being able to just swipe it with a flick of the wrist.
Another problem with themes related to the aforementioned one is that when a theme has rounded corners (or even more irregular shapes), it makes taking screenshots more difficult because even when you use Alt-PrtScr, the background shows through. (Look at all the Windows 7 screenshots where you can see through the rounded corners and even worse, through the translucent borders to whatever is beneath.) Most people don’t even pay attention to the issue (granted, it’s not usually a big information leak), but for those that do, it makes it a lot more work than just grabbing a shot of a nice, even rectangle.
Another issue is that themes are just fat. The Classic Windows theme is simply thinner and takes up less space than other themes—the vast majority of themes are thick for some reason, with the rare one that is thinnner. (In Windows 7, you have to set the taskbar to small icons to get it to stop looking so stupid and tall in Classic Windows mode.) It’s no secret that reducing the chrome is the current (and probably continuing) trend in user-interface design, so having thick, showy borders is merely a novelty.
It’s no surprise that themes also use a lot more memory than basic chrome. Themes have fancy shading and textures which require a more memory to store than a simple, solid-colored rectangle. As a result, themes take up more memory (maybe not a ton more, but more nonetheless), and so depending on the amount of memory in the system and the running applications, it can contribute to a reduction of available memory and cause unnecessary paging which of course has a direct performance impact.
Finally, I find that whenever I try a theme, the novelty quickly wears off and I get bored of it. I don’t recall how long it took to get bored of Luna, but I really did like Windows 7 for some time (about a week or two). However, I eventually stopped noticing the things I liked about it, so there was no real reason to keep using it. Once I switched to Classic Windows, I stopped noticing the chrome of the UI just as quickly, and now I focus on what I’m actually doing in Windows as opposed to what it looks like. I know some people call it ugly or old-fashioned, but it’s more streamlined for better productivity and it’s only ugly if you use a bad color scheme (each new version of Windows updates the Classic Windows theme with a smoother palette so it automatically looks newer, not old).
So in summary, it depends on the system and the user. For people who like to trick out their cases with colors, shapes, and lights, for those who like to post screenshots of their fancy-looking desktops with wallpapers of dragons and naked ladies, and for those with super-fast systems, then go ahead and use a theme if you like. But for those with slow systems or people who use computers to do things (ie, the computer is a tool, not the focus), then there’s little reason to bother with a theme; it doesn’t exactly make the OS any easier to use or more user-friendly regardless of whether you’re a novice or a pro.
Don't forget classic theme works much better over Remote Desktop for obvious reasons. – None – 2014-08-13T17:38:48.610
4My own opinion is that you will not see a difference in performance, unless it is really time (or many years past the time) to invest in a new computer. – harrymc – 2011-10-30T17:42:21.843
I don't really understand, why don't you just try it and see? – user541686 – 2011-11-04T18:36:57.737