A PNG can be a better choice
Because the PNG format supports transparent backgrounds, PNGs can be smaller than JPGs. PNGs are better for crisp graphics because there are no artifacts from data compression often seen in JPGs. (PNGs use lossless data compression and JPGs use lossy data compression.) Here’s a 25 KB PNG image at 96 ppi with a transparent background.
The JPG version from the same PSD file is over three times the size of the PNG at 86 KB and this is with a quality setting of 7 for the JPG.
Note the artifacts in the JPG below.
One final note, PNG files are generally useless to image thieves because they don’t know how to use them.