Budget Quad vs. Quality Dual Core

[Rdmkr]

It's always hard to make comparisons between these... I'm concerned with two cases in particular:

Dual Core Qualcomm Krait 1.5Ghz (Haier W910)
vs.
Quad Core MTK6589 cortex A7 1.2Ghz (Cubot GT99, etc)

and

Dual Core Exynos cortex A15 1.8Ghz (Voyo A15 tablet)
vs.
Quad Core Rockchip RK3188 cortex A9 1.6Ghz (Rockchip tablets)

DMIPS/Mhz stats are:
cortex A7: 1.9
cortex A9: 2.5
Krait: 3.3
A15: 3.5

so based on DMIPS the first comparison is 1.5x3.3=4.95 vs. 1.2x1.9=2.28; ratio 2.17:1
second comparison: 1.8x3.5=6.3 vs. 4; ratio 1.575:1

The question is, of course, how much difference the doubling of the cores makes in practice. The theoretical maximum is performance x2, but this is not always achieved. I guess in the first comparison we would say even in the best case, quad could not beat dual, right? The ratio is >2:1.

ps. antutu displays 7000 vs. 13000 as results for Haier W910 and Cubot GT99... which makes me suspicious of that test.

pps. even if the MTK Turbo processor gets 1.7 times the performance gains from its extra cores, the dual core Krait is the same speed as it... and that krait processor is in a phone worth $130. is this the most underrated phone on the planet or something? based on DMIPs alone you'd get that impression.