My own machine isn't heavy duty, but from my understanding heavy duty machines have stronger motors and can sew through more layers than usual, which I assume will lead to the machine getting stuck less often. My non-heavy duty singer machine normally runs great, but betrays me when I try to sew 4-5 layers of minky fabric when making plushies. It might be worth getting the singer heavy duty if you wanna make thick bags that use lots of layers or clothing that uses tons of thick fabric like denim. If it fits your budget I'd say go for it as long as you are buying from a reputable shop with warranty and refund options.
From the pic you've posted I don't think this machine has multiple speed settings. It's something I really wanted before I actually bought my machine and was sad mine didn't have it, but after actually using my machine I don't feel the need anymore since it only sets the max achievable speed, the foot pedal is actually what one uses to control the speed by applying different amounts of pressure. The speed of the sewing also changes based on your stitch length and fabric type, my motor sounds ready to croak when I sew small stitches on multiple layers of minky lol.