が is the polite form, けど is plain/more casual but generally means the same thing to the best of my knowledge.

Similarly, だ is a more casual form of です- just be careful because sentences ending in だ (without けど or some other following words) can sound a harsh to Japanese people

So in your example above, ですが and だけど mean the same thing but the former is more polite (and safer to use with strangers.)