Re: How about an octal-core ARM based laptop/netbook?
There is no power efficiency advantage in theory in either direction. The CPU ISA on either chip, if having same adequate resources, process node etc would come out roughly similar in speed and efficiency.
Intel 'wins hands down' as you say purely because they have been building Server Chips for a lot longer than ARM and have a more mature architecture in this respect
ARM are catching up fast with the recently announced next generations AppliedMicro X-Gene 3 and Cavium ThunderX2 arriving in same performance envelope as the middle range Intel xenon designs
What is just as important is the various ecosystems that support and create 'moats' against competition.
Intel arguably discovered this when trying to compete with ARM in the Smartphone. They also failed over a number of years to pull off an integrated modem solution which is vital for SOC mobile acceptance.
ARM in reverse has to compete with the Intel/Microsoft 'moat' and Server Software which has allowed Intel a near monopoly status in CPU Server market. If there was a genuine competition Intel wouldn’t be able to charge their eye watering (Server) prices. AMD is certainly a problem here at failing to offer genuine performance on their current line up of CPUs. Perhaps Zen will be different,