With the new release of Opera 10 Beta2 and K-MeleonCCF ME 0.096 coming out, I decided to make a simple test of both browsers.
I) Memory UsageFirst I am concerned of memory usage cause it's crucial for older system on which both browsers are popular.
1. Startup memory usage
At startup with no tabs open, K-Meleon cost less memory than Opera:

2. One website memory usage (www.cnn.com)
For testing the memory usage for just one website open, I delibrately open www.cnn.com to see which browser cost more memory:

K-Meleon only consumed half of the memory of Opera 10.
3. Several website memory usage
To see which browser can handle better memory usage when several websites open at the same time. I openned 6 websites:
[
www.cnn.com]
[
www.msnbc.com]
[
www.yahoo.com]
[
www.msn.com]
[
www.apple.com]
[
www.nba.com]
together in both browsers, here is the result:

K-Meleon has better performance than Opera 10
4. Memory release performance
It's also important for browser to release memory when tabs are closed. So I closed all tabs in last test, the memory usage of both browsers after this is as follow:

K-Meleon has better performance than Opera 10
II) Javascript performanceThanks to the latest treacemonkey js engine from Mozilla, K-Meleon's JS performance is more superior than Opera 10: (Test page: [
wd-testnet.world-direct.at])
III) CSS Loading performanceOpera 10 does have some speed advantages over K-Meleon, like CSS loading performance, with the test page:
[
www.howtocreate.co.uk]
Opera 10 is a little faster than K-Meleon:
IV) Results From data above, you can see that if you have an older system with slower CPU and less memory, you want to use a fast, responsive and very customizable browser, K-Meleon is much better choice than Opera 10 in this sense.