I have a Brother SE 270 and I only use different bobbin thread if I am embroidering a design that is really dense or uses a lot of thread on top. In that case, I use "bobbin thread" in the bobbin. You can buy it at Joann's and I used to be able to also find it at Walmart.
Otherwise, I use the same thread top and bottom if I am just sewing or piecing.
I haven't had any issues this way.