ちょっと、お聞きしたいんですけど (polite)” or "ちょっと、うかがいますか？ (very modest used in a certain business occasion ) Both mean the same thing but there's the difference of location to use the phrase. うかがう　is Kenjyo-go of 聞く　and Kenjo-go is one of honorific expressions and it makes an effect that it sounds modest and speaker is the lower position to the conversational partner at the same time. so Kenjyogo is used to talk with boss or upper-positioned people here in Japan. Therefore the second expression you said should be used in strict business occasion (such as the bank officer , call-center agent ...etc ). but for blue-worker , the former is the better. Too modest is not always accepted depending on a place. check here(and you should remember Kenjyogo-Sonkeigo ) :))) http://www.google.com/search?hl=en&q=Kenjyogo&aq=f&aqi=&aql=&oq=&gs_rfai= Good luck :))

どちらも同（おな）じ意味（いみ）です (Both is the same meaning) ですが，どちらも知（し）らない人や上司（じょうし） に話しかけるときの表現（ひょうげん）です (but it use when you to ask to strangers or boss) 親(した）しい人には，「聞きたいこどがあるんだけど」などというといいです：） when you ask to intimate person, 聞きたいことがあるんだけど

どちらもbetterですが、ちょっとを少々に変えたほうがよいです^^