Surface Pro 2.5 i5 4300U 1.9 Ghz 2.5 Ghz

Dude, the point of this thread is, you just paid the same price for a slower and less feature packed model of the same device. Based on the comparison chart a user posted earlier, there are lots more differences than just the speed...here's the comparison, most of it is enterprise/power-user stuff, but still a lot of improvements at no extra cost.

The "Haswell" series run cool.  All three processors (i3, i5, and i7) are LGA 1150 and all three use the same memory.

All three are energy efficient and all three are also installed in laptops.  I have the i5 4200U in a desktop right now that I scratch built and I can instantly, remove the processor and put the i7 in it.

You will lose about an hour or hour and a half on your battery if it was in the tablet.  The machine will not run hotter.

Intel stopped making the 4200U and are not available and the 4300U was its replacement.  It is a fraction faster.

This is not the only thread here on the forum regarding the 4300U but not once has anybody asked about the i7.  Not one of you.

Here is a thought for you performance geniuses, how come nobody ever asked for the Intel Core i7 "Haswell"?

If you are going to "upgrade", then upgrade!  Don't stick with the same processor class.  The performance difference between the 4200U and 4300U is that the 4300U can draw pretty pictures about 1.5 seconds faster.  And that is about it.

I got a chance to compare the two with two different desktops yesterday when I was setting them up for use for other people and thought to set them side by side and compare them.

You will get the same performance from the tablets as well since they both have the same motherboard chipsets and data buss speeds.

Those machines are now in the hands of their owners and didn't have the time to do screenshots of the performance ratings and if I did, I would post them here.

If you are going to spend money and time on an upgrade, go for the next higher processor and not a slight upgrade of the current model.

Wonderful! We have an expert to help us who has compared the Intel chips and come to a quantitative conclusion! Please, direct me to where I can find this Core i7-equipped Surface Pro 2, and I will gladly throw money at it!

Edit: Assuming that you are talking to Microsoft instead of all of us while lecturing them on the speed differences between different classes of chips, a few reasons that they wouldn't go with an i7 might be battery life, thermal and space constraints, and price given that ultrabook i7s probably aren't in as much demand as the i5s.

Here is a thought for you performance geniuses, how come nobody ever asked for the Intel Core i7 "Haswell"?

If you are going to "upgrade", then upgrade!  Don't stick with the same processor class.  The performance difference between the 4200U and 4300U is that the 4300U can draw pretty pictures about 1.5 seconds faster.  And that is about it.

I got a chance to compare the two with two different desktops yesterday when I was setting them up for use for other people and thought to set them side by side and compare them.

You will get the same performance from the tablets as well since they both have the same motherboard chipsets and data buss speeds.

Those machines are now in the hands of their owners and didn't have the time to do screenshots of the performance ratings and if I did, I would post them here.

If you are going to spend money and time on an upgrade, go for the next higher processor and not a slight upgrade of the current model.

Uhm, you from the future? It's still 2014 here, and as you stated, first two digits imply the year. So, unless the first 2 digits don't actually imply the year they were built in OR you time traveled, doesn't make sense to have lot number that starts with 15.

According to comments in this thread, the safe bets for the new processor are 1351+ lot numbers; all 14XX lot numbers come after that.