Not sure what smell you are experiencing, but this is my very first batch and I am doing 5 gallons in a 6 gallon bucket, and not noticing any weird smells... just pretty "normal" yeasty ones, like what I would smell while letting bread dough rise. I definitely get a hint of banana as well, but nothing super strong or overwhelming or unpleasant...
Could the smell just be that you have more gas built up and concentrated in the bucket than you would in carboy? (I'm assuming your bucket holds a greater volume than your carboy does. For example, I am doing 6 gal bucket but will rack to 5 gal carboy... in this scenario, when I remove the lid I am going to be facing something like 5x-10x as much built-up gas as I would be if I had filled up the carboy with the same volume)