Re: Aikido v.s. Hapkido
A couple of quick points:
There is no documentation (as someone else mentioned) that the founder of Hapkido ever studied with Takeda Sensei. Takeda Sensei kept EXTENSIVE log books of who trained with him and when. Choi (or anyone like him) is not found in those books. The stories floating around about him being a house boy for Takeda have so far proved to be completely bogus. This does not mean that Choi did not have exposure to Daito ryu from one of Takeda's students. The similarities between some versions of the arts do seem to be significant.
Aikido at least varies widely between styles and dojo. You should survey the ones in your specific area to find out what they do. I'm sure much the same can be said of hapkido. For instance, some have mentioned (positively and negatively) the "spiritual" focus. Yoshinkan Aikido (from Gozo Shioda, a long time student of the founder of aikido) is very physical, very demanding, and does not push spiritual or religious teaching at all. In fact, many of the Shinto rituals associated with training in Japan and Japanese arts have been stripped out, as Gozo Shioda was not a particularly religious man. Yoshinkan aikido is perhaps the second largest world wide affiliation of aikido schools.