Understanding Laptop CPU Performance & Battery Use Diffe

[consultant]

I have a laptop with a Core i5-2520M. This has a Passmark benchmark of 3536 and a max TPD of 35W. I want to get a new laptop that has at least 25% higher performance and a lot longer battery life. I've examined Passmark ratings and TPD ratings and it appears I have two main choices:

a) Get a 35-37W Quad Core Processor with twice the Passmark benchmark as my current CPU and about the same power consumption. Examples: i7-4712HQ (Passmark 8270 37W), i7-3632QM (7004 / 35W)

b) Get a 15W Dual Core that has roughly half the Passmark. Examples: i7-4510 (3951 15W).

I'm mainly a business user but I will eventually be doing some video editing so I'm leaning towards the quad core.

Seing that the max TPD of the Quad Core is about the same as my current CPU. All other things being equal (power draw of the other components and battery capacity), would I still get longer battery life because on average the newer Quad Core will not being using all cores so the power consumption for the same tasks (web browsing, etc) would be less than the older i5 with the same max TPD but with half the Passmark?

I read somewhere that a lot of laptops or apps don't even take advantage of the four cores? Is that true?

Basically I need to confirm the Ivy Bridge i7 Quad Core is essentially much more energy effecient than my older Sandy Bridge i5. Either I want signifanctly better battery life with the same performance when the i7 isn't using all the cores, or, siginificantly better performance for CPU intensive operations but with about the same power draw. The specs seem to indicate that but I'm not sure if everything works out linearly as I'm assuming?

[Guest]

First of all, you have to check if you have the BGA version or PGA version of i5-2520M. If you have the PGA version, it uses the G2 socket and you have no chance to put a mobile Haswell processor (like i7-4712HQ which is anyway a BGA version) that uses G3 socket. The best processor you can put if you have a PGA version processor is an Ivy Bridge generation processor (but only if your motherboard support it). In this case, it is better to use a processor that has no more than 35-37W (your notebook was made having in mind a certain thermal dissipation).

[gshv]

You cannot put 4th generation processors in laptops, designed for 2nd and 3rd generation processors. They use different types of sockets.

Gennadiy