Likeability is extremely important, no doubt. The product has to be what a prospect needs but he will buy it from who he likes for sure.
I try to hire different personalities (assuming general traits shared among sales people).
I've split the US in to five regions and they all focus on one region, broken to sub-regions, at a time. As we get to the end of the prospects, we move to another region.
By the time we go full circle, enough time has passed that I rotate the sub-regions so that a new personality can make new connections with prospects who did not become our vendors during the first sweep and won't remember my company specifically.
Varying personalities are crucial to keep every "territory" from ever going cold. My guys need to be technical too though, and they need to follow my program age be damned. It's ridiculous how many old dudes work for me, knowing full well I'm the boss and owner and develop shitty attitudes. It's all "yes sir" "no sir" " I don't care who I work for sir, every company has it's process and I'm a team player" when they need a job.
Then I hire them and they develop some age complex and are totally shocked when they get fired.
I don't fire people for fun either. If some one is not producing but following my system I work with them, give them time, let them shadow my successful people, I don't tolerate intentional disobedience however, personality be damned. I can't. Being young, if I did, all my guys would try to walk on me and I have to have my stables full. I can't afford to fire every one at once and start over cold so I can't let weeds grow.