There are a ton of threads from the last 24 hours asking similar questions.
The best answer I've found so far is from:
So $1499 13" is the best bang for the buck?
https://forums.macrumors.com/threads/1657556/
But here's some extra info I dug up via Wiki regarding the processors (the MHz numbers represent GPU clock speed):
- i5 2.4GHz = Iris 5100 (GT3) | 1100MHz | 3MB L3 | +$0
- i5 2.6GHz = Iris 5100 (GT3) | 1200MHz | 3MB L3 | +$100
- i7 2.8GHz = Iris 5100 (GT3) | 1200MHz | 4MB L3 | +$300
So essentially you can get the higher GPU clock speed for an extra $100, but lose out on the additional L3 cache (which can be fairly important for CPU intensive tasks). An additional $300 seems too much for the i7 for my uses, that's for sure.
And Geekbench scores tell you % wise what the difference is:
13-inch with dual-core CPU:
- i5-4258U @ 2.4 GHz: Single-Core 2613, Multi-Core 5248
- i5-4288U @ 2.6 GHz: Single-Core 2856, Multi-Core 5954
- i7-4558U @ 2.8 GHz: Single-Core 3000, Multi-Core 6189
Per these scores:
Comparing the
2.6 i5 to the
2.4 i5:
- 9.3% faster for Single-Core
- 13.5% faster for Multi-Core.
Comparing the
2.8 i7 to
2.4 i5:
- 14.8% faster for Single-Core
- 17.9% faster for Multi-Core.
Comparing the
2.8 i7 to the
2.6 i5:
- 5.0% faster for Single-Core
- 3.9% faster for Multi-Core.
So the 2.6 GHz i5
definitely seems to be the best % increase per $. Both the 2.6 i5 and 2.8 i7 give you the 9.1% speed boost to the Iris 5100 graphics frequency over the 2.4. The i7 also gives you 25% more L3 cache, which may be useful depending on how CPU intensive your work is.
I'm in a similar situation trying to decide what I want. I know I'm at least buying the top-end 13" configuration (2.6/8/512 for $1799). I can't decide if I want to spend the extra $200 each for 16 GB of RAM and/or the upgrade to the 2.8 i7.
On the one hand, I doubt really think I need either upgrade for my planned uses: browsing, document creation, editing photos and short videos for a blog,
maybe the occasional windows GPS trip planning software via VMWare Fusion. Buying a "stock" model means I can pick it up in store, and should I have warranty issues get a replacement more quickly.
On the other hand, I would be annoyed if in a couple years I'm running up against RAM or CPU limits, and need to replace the machine with a new one...
I'd like to buy soon, but don't need to immediately. I can wait to see video benchmarks and learn if there's any speed differences between the 2.6 i5 and 2.8 i5 in terms of the Iris 5100 performance.
