Spiders are cute.
Anyway, just make sure it fits anatomically, IMO: Legs have 7 segments (you can get away with 4, and most people won't know), all attach to the cephalothorax (also the eyes and fangs go here)
Hairy: make it more Tarantula, bigger cephalothorax (3/4 size of abdomen), beefier legs, don't forget the pedipalp which are clear and easily seen (appendages near the mouth/fangs) and usually held out in front of the spider to grab and hold secure and long, as the venom is more a slow death. Legs REALLY need 5 segments. Femur length = Cephalothorax width. All other leg segments roughly 1/2 femur width. Overall (rear) leg length should just reach the end of the abdomen. Don't forget the carapace on the top of the cephalothorax.
The shiny black: go for the Widow look. Cephalothorax at least half the size of the abdomen, but they should be even along the bottom, so all the size of the abdomen is added height. Pedipalp are small, to the point of being left out if you want, and are held like a mantis' arms, ready to strike swift and let the paralytic venom do it's thing. Femur length roughly = abdomen length. If doing 4 segments, each additional one roughly = 3/4 the length of the one before it. (for 7, the last 3 should total 3/4 of the 4th segment) Remember there IS still hair, and some strategic single hairs could be really creepy.
Or just figure the entomology hobby is well too prominent in this insane person...