I got it. The geekbench difference was about 12%, and since the graphics is integrated, I figured I would do as much as I could to give the HD4000 some horsepower to run off of. Not sure if it will actually make a difference, but it made me more satisfied.
Only you can decide if it is worth it. If you do CPU heavy tasks, the answer is probably yes. If you don't push the CPU very hard on your systems, then save your money and get the i5. Then again, I'm sure the i5 would perform admirably.
Real world benefit beyond compiling software, processing movies, music or pictures, or playing some games (etc.) will probably be unnoticeable between the i5 and i7.
If you plan to purchase the retina 13", yes it's overpriced but if you want that portability with the added retina screen and you do not plan to upgrade for a long while, then yes go for it if you got that $$ to spend.
Since they don't offer a 16gb upgrade for RAM which in imo is massive deal breaker for a lot of users considering 16gb is pretty much the norm these days even though most will likely not utilise it, 8gb + SSD is more than adequate.
So, honestly, if you got the $$ and want the max performance you can get and you do not plan to upgrade for a long while, go for it. You can't upgrade the the cpu. Whereas I assume you can upgrade the SSD, not sure if OWC ssd for retina is compatible with the 13",
if it is it might even be cheaper to just upgrade the CPU and stick with the 128GB and purchase the 480GB OWC SSD and upgrade yourself.
You'll have to find out if it's compatible, I'm just giving you options here.
Otherwise, if you do plan to upgrade or even considering the 13" retina for only a shot period, I honestly do not think it's even worth purchasing.
Even by upgrading the cpu, you probably will not even notice the increase in speed unless you're really picky.