[mru]

ARMv7 has a SIMD unit (NEON) that easily outshines SSE and Altivec. Floating point support is also good nowadays.

[DarkShikari]

Or, better said, the instruction set NEON outshines SSE and Altivec. The actual vector unit is a bit lacking performance-wise by comparison, which shouldn't be particularly surprising given that it runs on 100 times less power.

[mru]

True, but there's nothing to say future implementations will not be faster. Adding more execution units is "easy". Fixing an instruction set is not.