Both great machines but it's the C64 for me due to like ipmarks said it's what my dad bought me for Xmas 84.. was getting a Speccy, but about 2 weeks before he cam in and showed me an advert in the paper for the C64 and said "What about this one? Is it any good?" Only one kid at that time at school had a 64 and I had played it and loved it but thought it was a bit too pricey for my old man.. but he liked the look of it himself and as an upgrade from an Intellivision he was all for it.. so a 64 was under the tree that year..
I was as excited as when he had come home from work one day and took the Intellivoice module and B-17 Bomber cartridge out of his brief case.. I almost fainted!
I love it for all the reasons that everyone above has said.. nothing to really add to the comments..
I do have a soft spot for the Speccy though as some of my mates had them and I really enjoyed playing on them.. and vice versa they liked playing on my 64... we all had banter about which was best but we all really liked playing on both of them so it was just that.. banter..
We had the next round of this with the 16bits.. me with my Amiga and them with their ST's..
I really miss those days.. sigh..