Which is better: Lenovo or ASUS?

In the past, I've owned laptops from as low as $200 to as high as $2,000. My main complaint with all these laptops is sluggishness, not to mention overheating as well. I've followed the experts' advice on how to maintain optimal performance, but such issues are evidently unavoidable.

I don't want to buy anymore HP, Acer, Dell, Compaq, Toshiba, and Samsung laptops. I'm considering Lenovo or ASUS.

Any comments on their respective performance and quality? If so, could you also offer a few models for consideration? I'm looking for speed, power, and durability. I'm neither a gamer nor a programmer. Basically, I want a laptop that isn't sluggish.

And if you think it's the operating system that's the culprit, please also suggest viable alternatives.

Added (1). When working, I have many windows and programs open. Perhaps I need to buy a laptop with high processing power and RAM.

Added (2). Actually, I do use compressed air to clean those sections. Thank you for the suggestion, though.

I do my best to select the best anti-virus software on the market. I used to have Lavasoft, but they went down in quality. Fortunately, the laptops I've owned rarely contracted malware and viruses. I defragment my drives and so forth.

Added (3). Yeah, they make anti-virus software too. I switched to Avast two months ago.

Actually… Lenovo and ASUS are both solid brands. Listen though, you HAVE to keep the CPU fan/heatsink free of dust and gunk or else ANY laptop will eventually overheat, Shoot compressed air into the vents every few months or so

You can get an Lenovo 14" now with a Core i7 3610QM + 640m GT video chip + 8 GB of RAM for $800-900. Y480. I almost got one myself but shipping is too delayed right now

As far as sluggishness goes, periodically defragment your hard drive, make sure you are running a decent antivirus at all times. Even download Malwarebytes Antimalware and do occasional scans. Not maintaining a Windows PC leads to problems

I didn't know Lavasoft made an antivirus. They make Ad-Aware which is for spyware

EDIT: In that case, malware/spyware is probably the culprit. I use free Malwarebytes Antimalware as well as Spybot Search and Destroy in addition to an antivirus. You do not have to keep them running all the time, just do weekly scans