One of the most important factors deciding whether or not listeners respond to a hip hop beat or not is whether it makes them move, and club beats are and have always been designed to make people get up and move. Just think about it. If people are sitting around bored at a club then the DJ isn't doing his job, so he's got to find music that'll make people get up and dance.
What this has to do with you is that if you can rap to a club beat, or to several club beats then you will gain exposure to an audience that you otherwise might not have gotten. Rapping to a club beat is also important because people tend to remember the songs with the beats that make them dance and if you can associate your song with the beat that made them dance then you have done a great deal in the battle to win over fans.
Being a rapper is much more than simply laying down hot verses. Don't get me wrong, having sick rhymes is absolutely essential to your success, but if you aren't going to rhyme over equally hot beats then you're lyrics are going to have little chance of being heard by any audience whatsoever. People generally judge a song by its beat in the opening seconds of the song, it's afterward that they may reflect on the lyrics, so it's especially important to grab them with beats even before you get to the lyrics. A weak beat will hurt a sick flow everyday of the week. And don't be fooled into thinking that club beats are somehow weak based simply on their genre. It is good for you to get your music into the clubs as soon as you can. And it doesn't matter if you offer up a few club songs to your repertoire or just remix some of your stuff over club beats, the point is that you have the material to cover any audience wherever that audience may be.
It's imperative to start putting down lyrics to club beats as soon as you can, especially if you're an unknown artist because based on the club beat alone people might listen to the song and then come to know you because of the beat you chose. You will also be able to work the club scene easier if you have a few tracks dedicated to it. Don't be fooled, club patrons buy music too, so be smart and make some tracks exclusively for them. You won't complain if you start making some money from selling your stuff to a club audience. Having some raps to club beats will also help you get your music played inside the club. And trust me, it's easier to pitch a DJ your song if it sounds like something he would ordinarily play. Then you can possible parley that airtime into a few sales at the door. Whatever you do, spend some time and put down a track to a club beat.