Longboarding is much easier in my opinion. Skateboards are mostly used for tricks, not so much cruising and it probably wouldnt help you with surfing as much as longboarding would. Longboarding was designed to help surfers and snowboarders to be able to practice or do there thing when there were no waves or snow. On a longboard you cruise, do tricks, bomb hills, and can also carve which is extremely helpful for surfing. You can find a good longboard anywhere between 90-250. My first one was only 70 and then I upgraded to a Kahuna for 220, I paid half and my parents paid the other half.
Longboards are better to learn for surfing in my opinion and you can pick up a good sector 9 for about $225 or so
since your a surfer, you should longboard. skateboarding is for like cruising and tricks. but if you just wanna cruise around, longboard cause you cruise on you surfboard too. so it's more sensible just to longboard.
These other answers explain it well, but if you are buying a longboard that intend to only cruise on, you get what you pay for.
