how do they do it? 4tc vs Clear Oval

Agree with Thorman,and :

1]oxidized terminals.You should only compare your new and old cables after thorough cleaning only,with stuff like deoxit and the likes.You would be surprised at how new and nice your old cables actually sound after a good cleaning job.

2]Demagnitised the the old cables first , before you compare.I know there are a lot of naysayers out there with regards to demags, but it could do wonders to rejuvenate your old cables.,think of it as sending your cables to a spa....

3]Newer connectors .Sometime all you need is 'terminal' upgrading rather than the whole cables itself.The WBT Nextgen series are just jaw droppers...

CHEERS

wait a month and switch back and see what you think, I have found the first impression often is the best but after a while you find out what is wrong with the new stuff (and things like fafafion points out) and the playing field is more even.