The Bersa Thunder .380 comes in 2 types. The Thunder .380 and the Thunder Plus. The big difference is the regular .380 has a single stack magazine, whereas the Plus version has a double stack magazine.
Personally, I have the regular version and am very happy with its accuracy and concealability. The double stack version approaches the size of the Thunder .45. For me, if I have to carry the equivilent size and weight, then I might as well step up the .45.
However, the .380 is a good compromise and is the pistol I carry most often.