Many of us could not afford Intel and the K6-2 was the underdog that could upgrade your old PC.

A Pentium II/3 is faster but depending on the software a K6-2 is more adjustable and configurable for a relatively wide range of old and pre 2001 Software.

So the question is, is it worth to use a K6-2 instead a Pentium III, why are Super Socket 7 mainboards so appreciated?

If we consider practical usage - they aren't, most of the time. Slot 1/Socket 370 platforms are very abundant and easy to use.

rmay635703 wrote on 2020-06-11, 15:27:

Many of us could not afford Intel and the K6-2 was the underdog that could upgrade your old PC.

A Pentium II/3 is faster but depending on the software a K6-2 is more adjustable and configurable for a relatively wide range of old and pre 2001 Software.

I had a K6/2 400 indeed, funny thing is that I got the Pentium II and III for free and now I'm paying for a used K6-2 (even when it was"only" 30 euros for the full tower)

Both! I strongly preferred Intel at this time over AMD because my attempts to use AMD stuff almost always ended with frustration over system stability. I'd buy parts with the best benchmarks which was almost inevitably overclocked, and suffer crashes and system lockups regularly as a result. I fled back to Intel motherboards with Intel CPUs and no overclocking after that. But I always appreciated the serious competition from AMD that kept the industry moving forward. So I'd take the K6-2 just as soon as the Pentium II/III because it equally represents computers of the era.

esbardu wrote on 2020-06-11, 15:09:

So the question is, is it worth to use a K6-2 instead a Pentium III, why are Super Socket 7 mainboards so appreciated?

To answer your question, specific Super Socket 7 mainboards that support K6 "plus" CPUs are very appreciated when paired with a K6-2/3+.
That's because these CPUs can be used as a sort of time machine, due to some unique capabilities (like the ability to change the CPU speed in software, disabling L1 cache while leaving L2 cache activated).
Because of this, you can progressively slow the CPU down to 386 / 486 speeds, which will allow you to play most speed sensitive DOS/early Windows games, while also being able to comfortably play more demanding games from 1998/1999 or even 2000 (depending on the game).
This is something that you can't really do with any other CPU/platform. For example, a Pentium MMX gives you a more granular level of slowdown control, however this CPU can struggle even with some late DOS games (not to mention games from 1998/1999 which are virtually unplayable)

But, I think that for many people, a Pentium 3 Coppermine/Tualatin is probably more suitable. It will still allow you to play many DOS games (and late DOS games will be blazing fast), while also being much more powerul than the slow SS7 CPUs, allowing you to play at high framerates most games up to 2000/2001.

A Pentium III is more comparable to the first round of Athlons, no?
Remember that back then AMD was more of a "budget" processor company with the K6-2 and K6 just like the 5x86, 386DX-40, and so forth before them. My school had some K6 or K6-2s (can't remember which). My cousin got the cheapest Compaq before heading off to college and I believe it was a K6. I wanted a K6-2 at the time! (never got one until years later off of eBay, but it is a +, so there).
Super 7 is kind of neat in it being the last time you could put both Intel and AMD CPUs into the same board.
Since you've got several similar machines perhaps mess around with different OSes on them? How about Win98SE on the Pentium III, NT4 on the Pentium II, and Windows 95 OSR2.5 on the K6-2.
The K6-2 and Athlon certainly played a role in pushing performance ahead and prices down. Imagine if Windows Me would have had to stick around a while longer for consumer computers to catch up to NT-based Windows...