x86-64 vs ARMv8-A

[Livy.]

I am going to get an ZenFone 2. Unlike most handsets out there, Asus chose Intel over ARM. However, Qualcomm and Mediatek versions of the ZenFone 2 are arriving in Q2 2015 at a lower price (FYI, several dozens of bucks is not very important to me).

This thread is not to start Intel vs ARM or CISC vs RISC war. I would like to hear personal opinions (based on technical knowledge) and experiences (based on real life usage), before I make a decision.

Personally, I do not like Intel at all. Intel's chips are not designed for mobile devices in the first place. x86 chips are powerful compared to ARM's because they can process complex instructions at hardware level, but they consume more power. I want to have a phone for prolong usage, not a supercomputer in my pocket with 1 day battery life.

The x86 architecture has a long history along with a heavy backward compatibility burden. Later Intel's chip provide new instruction set extensions (SSE4.2, AVX, FMA4...), while maintain backward compatibility with old software by supporting all previous instruction sets (MMX, SSE2, SSE3...). Even the x86-64 chips are not a clean design from the ground up, but rather an extension of the x86 developed by AMD. It will no doubt increase the cost and reduce performance.

ARM's chips, as far as I know, have no such thing. The ARMv5, ARMv6, and ARMv7-A are totally different and are not compatible with each other. The new ARMv8-A are backward compatible with ARMv7-A, but through some mode which is said to maintain a clean design, while does not affect performance.

Which version of the ZenFone 2 is better for software in general, and for PPSSPP in particular, Intel or ARM?