There is very little I can add that hasn’t been said about the performance of our processor compared to the one in the surface.
Indeed, their Ultrabook-class ‘U’ CPU has a potential for greater sustained performance. During those spikes that you mention, though, they will perform quite similarly. Both the 2-in-1 class ‘Y’ processors and ‘U’ processors can provide serious performance when called upon. The advantage of the U-class CPU is that it can maintain that performance level for longer at a time.
As both CPU types are aimed at thin-and-light devices, with power saving taking priority over processing power, the performance outside of sustained processing workloads is nearly identical.
Using more power also means the chip generates more waste heat, and this is where we see the downside of pairing a U-class CPU with a fanless design: even though the CPU could sustain high performance, thermal limitations will still keep it from maintaining higher clock speeds over time. In the end, though the Surface is equipped with a technically more powerful processor, the way it’s implemented makes it so that in practice it will not perform much better than its Y-class equivalent in the V.
Meanwhile, the V’s CPU is designed to be more power-efficient, which is a benefit you can see reflected in its battery life compared to the competitor from Microsoft.
(And as for the comparison to desktop CPUs, not even the H-class – which offers an almost even balance between processing power and energy savings – can measure up to the S, K and X-classes aimed at the desktop and high-end-desktop segments. These were designed for processing power above all!)
Now, m3 vs. i5… It really depends on what you plan to do with the device! If you’re looking to use it for office work or content consumption, you will notice no difference between the m3 and i5 model. So if that’s all you need, you can save a bunch of money and choose the m3!
Or, if you will, “if the above applies to you, then take the m3, you will be happy!”
In gaming the i5 may have a slight performance advantage, though both will only lend themselves for entry-level gaming or heavily optimised titles like eSports games. In content creation like photo and video editing, the i5 will see a bigger performance improvement of up to about 20%. Very heavy Excel sheets with thousands of lines with references and formulas may also benefit from the i5. If you are into having tens of tabs open at once in Chrome, you may benefit from the i5 model with doubled RAM, though that, too, comes at a cost. And of course, the i5 is a good option if 128GB of storage is not enough for you!
Luckily we live in a time where really slow computers are hard to come by. Unless you really want to save a buck and buy Intel’s N-class CPUs: the dreaded Atom. Where Y combines performance and battery life at the cost of price, N combines price and battery life at the cost of performance…