Surprisingly seems that fourth generation of iDevices is slower than third.
I tested my game on iPod Touch 4gen, which is considered as the same as iPhone 4 (which has only more RAM) and I got 9 FPS.
In my game I'm using blob shadows not only because of performance reasons, but also it just goes with simple comic style. But I found it's the bottleneck, at least for Unity projectors, so after removing shadows I got 16 FPS, which is still poor, but performance raises almost twice.
Well, what about iPhone 3GS then ? Works perfectly in 30 FPS with full details, which gives me two new thoughts - because of low resolution it's faster than iPhone 4/iPod Touch 4, and because it's stick to 30FPS, and rendering is v-synced, seems 3GS screen has 30 Hz refresh rate not 60. Frankly I can't find any information about this.
I gathered information from internet (I hope it's precise enough) and sorted Apple models from slowest to fastest. I'm not Interested anything before iPhone 3GS, because it was first (world first?) mobile with "real" GPU.
Ofcourse it's not that easy to say which hardware parameter is most important, but for 3d game say it will be GFLOPS and GPU model/family.
 A4 1.6–2 GFLOPS:
- iPhone 4 / Apple A4 800 MHz (ARM Cortex-A8) / PowerVR SGX535 / 512 MB RAM / 960x640 24 bit
- iPod Touch 4 gen / Apple A4 800 MHz (ARM Cortex-A8) / PowerVR SGX535 / 256 MB RAM / 960x640 18 bit
- iPad / Apple A4 1 GHz (ARM Cortex-A8) / PowerVR SGX535 / 256 MB / 1024x768 24 bit
(iPad 1 has 200Mhz more but with bigger resolution I think actually it's the slowest device)
 1.2–1.6 GFLOPS:
- iPhone 3GS / S5PC100 600 MHz (ARM-Cortex A8) / PoverVR SGX535 / 256 MB RAM / 320x480 18-bit
- iPod Touch 3 gen / S5L892 600 Mhz (ARM-Cortex A8) / PowerVR SGX535 / 256 MB RAM / 320x480 18-bit
(With that low resolution that devices actually are surprisingly good).
 A5 14.4 GFLOPS:
- iPhone 4S / Apple A5 800 MHz (ARM Cortex-A9) / PowerVR SGX543MP2 (2-core) / 512 MB RAM / 960x640 24 bit
- iPod Touch 5 gen / Apple A5 1 GHz (ARM Cortex-A9) / PowerVR SGX543MP2 (2-core) / 512 MB RAM / 1136x640
- iPad 2 / Apple A5 1 GHz (ARM Cortex-A9) / PowerVR SGX543MP2 (2-core) / 512 MB / 1024x768 24 bit
- iPad mini / Apple A5 (?) Ghz (ARM Cortex-A9) / PowerVR SGX543MP2 (2 core) / 512 MB / 1024x768 24 bit
(Starting from A5 chip - now we can talk, newest iPod Touch also belongs to this family so it's not like iPhone5 but like 4S)
 A6 27 GFLOPS:
- iPhone 5 / Apple A6 1.3 GHz (Swift ARMv7-A) / PowerVR SGX543MP3 (3-Core) / 1 GB / 1136x640 24 bit
(A6 is slower than A5X, this is obvious but can be surprise for many people, still iPhone 5 has lower resolution than iPad 3)
 A5X 36 GFLOPS:
- iPad 3 gen / Apple A5X 1 GHz (ARM Cortex-A9) / PowerVR SGX543MP4 (4-core) / 1 GB / 2048x1536
(I hope that new Mac Mini will be shipped with retina and A5X it would be perfect)
 A6X 80 GFLOPS:
- iPad 4 gen / Apple A6X 1.4 GHz (Swift ARMv7-A) / PowerVR SGX554MP4 (4-core) / 1 GB / 2048x1536
(Real monster, 80 GFLOPS, do we need for gaming PC or consoles anymore ?)
For comparision, I found something about consoles
- XBOX: 5.8 GFLOPS
- XBOX 360: 115.2 GFLOPS
- Dreamcast: 1.4 GFLOPS
- Wii: 2.9 GFLOPS
- PS2: 6.2 GFLOPS
- PS3: 218 GFLOPS
Correct me if I found wrong numbers. Thanks.