They both have their uses but you need to understand the principles they work on.
Bollinger – channels based on standard deviation
Keltner – based on average true range (volatility proxy).
Neither is "better" than the other – they are both just tools which can be useful if you have a particular purpose in mind. I would suggest a detailed study of what they are and what they can be used for (investopaedia is a good start) and then you can decide if they are of use to your style of trading.
Bollinger bands are just another one of the myriad of indicators and in the right circumstances can produce good results. I would suggest that one of their most apparently underrated uses is to measure the standard deviation of any particular variable you come across in your trading. In Metastock (I quote that because that's what I use and am familiar with) you can lay an indicator (Bollinger for instance) on to another indicator or variable – that's a very useful facility and presumably any worthwhile package would include it. So, eg. if you trade pullbacks, Bollinger's standard deviation can tell you "how much of a pullback" you are experiencing. That is useful information. (You could also achieve the same result by feeding data into a spreadsheet – but it's a lot more tedious). And of course, some traders may well be able to just look at the chart and make a good "gut feeling" assessment: but I like to deal in figures because they can be quantified and potential trades can be ranked! A good understanding of standard deviation and how to use it in trading has been a worthwhile investment in my experience - and Bollingers are an easy way to use it.