Which company should I use for domain registration and/or hosting?

May I suggest not GoDaddy whose CEO has made a spectacularly bad PR decision.
'... CEO Bob Parsons phoned in, Charlie-Sheen-style, to dig an even bigger hole for himself after the Zimbabwe Elephant Killing Debacle. The poor, starving African villagers he left the carcass to should be grateful, according to the CEO, because elephants are "a valuable source of protein." Well, by that logic, so are CEOs.

Warning: This video includes scenes of a dead elephant and are quite distressing.