Pc for me, a beast of a pc is far cheaper than a decent mac. Cheaper to fix and upgrade as well.
Macs do seem to have a good name for longevity. There are not many 5+ year old pc's around that are running almost as well as the day they were bought. I have heard a few mac owners state they have fully functioning machines many years after purchase. Another plus is that macs don't seem to be targeted by viruses as much.
Saving £20 a year on internet security and their longevity still doesn't justify a macs stupid price tag for poorer specs. Take the 8 core mac pro at £2799 as an example of stupid pricing, its specs are less than my £1200 pc base unit. All that extra money and you only get a 1 year warranty and 90 days telephone tech support, wow. It amazes me that people pay the ridiculous prices.