Let's not fall prey to the megahertz myth, shall we? 268MHz doesn't mean anything of value in terms of performance assessment when we don't know how many operations per cycle the system performs to begin with - we don't have access to exact benchmarks, we're merely working with values available online for the ARM11 line.
The second myth we have to bust is that the original 3DS used only one core in games - that's not true, at least not anymore. This was a limitation when the system was first put on the market that's been eliminated since - the OS uses only a portion of one core and the system is fully capable of running multithreaded applications. It's not entirely fair to say that 4*268MHz is equal to 2*536MHz, it's not that simple, but I think it's safe to say that we're looking at an almost 100% increase of firepower here, I'm saying almost because some will be lost for the sake of code parallelism. This is a pretty substantial increase, we can't pretend that it isn't.
As far as Integer versus Floating Point maths are concerned, Floating Point is rarely performed on the CPU these days - systems either have dedicated maths co-processors or simply calculate Floating Point on the GPU, so arguing over whether the Floating Point performance of the CPU is better or worse than that of the Wii's CPU is pretty pointless. Moreover, we can't forget that we're talking about a portable device that runs at a lower resolution than the Wii itself - it doesn't have to match the Wii's performance 1:1 to support the same or similar quality software, at least in terms of visuals.
Lastly, it's worth to mention that althought the Wii might've been better at number-crunching, the 3DS supports more contemporary hardware accelerated effects, it's simply a more modern design.
The second myth we have to bust is that the original 3DS used only one core in games - that's not true, at least not anymore. This was a limitation when the system was first put on the market that's been eliminated since - the OS uses only a portion of one core and the system is fully capable of running multithreaded applications. It's not entirely fair to say that 4*268MHz is equal to 2*536MHz, it's not that simple, but I think it's safe to say that we're looking at an almost 100% increase of firepower here, I'm saying almost because some will be lost for the sake of code parallelism. This is a pretty substantial increase, we can't pretend that it isn't.
As far as Integer versus Floating Point maths are concerned, Floating Point is rarely performed on the CPU these days - systems either have dedicated maths co-processors or simply calculate Floating Point on the GPU, so arguing over whether the Floating Point performance of the CPU is better or worse than that of the Wii's CPU is pretty pointless. Moreover, we can't forget that we're talking about a portable device that runs at a lower resolution than the Wii itself - it doesn't have to match the Wii's performance 1:1 to support the same or similar quality software, at least in terms of visuals.
Lastly, it's worth to mention that althought the Wii might've been better at number-crunching, the 3DS supports more contemporary hardware accelerated effects, it's simply a more modern design.