Definitely a hen. Do not get a male. They are fine when young but turn into biters and holy terrors by the time they are about 8 to 10 years old (depends on the husbandry) when they reach what I call the 'age of sexual frustration'. Sennies are nippy birds, all of them, males and females. The females can be very affectionate but they are also stubborn little things who want their way and have no problem whatsoever giving you a love bite if they don't. They are not usually bad, they don't even break the skin but they can hurt a bit and, most of all, startle you. But the older males are mean, mean, mean. I am talking completely fearless and almost incorrigible little birds that will keep on coming back to bite you and figure out ways of doing it when you try to prevent it (like coming from behind when they figure out that you duck if they do it from the front and grabbing onto the top of your head, lean over so they can bite your face). And boy do they bite hard! They might be little but they pack a wallop in those little beaks and I have the scars to prove it! They also don't let go and hang on to your flesh like a little pitbull even you might pull and pull
Don't misunderstand me, I love senegals. I think they have incredible personalities and I admire them intensely! These birds are good eaters, good bathers, hardy, beautiful and very intelligent. I love their 'never say die' way of approaching life and I happen to think their little dances are the cutest thing. But the males all end up as biters so get yourself a female.