It really depends on what you're looking to get out of it to determine which one is best. Being new, I'd probably point you towards HAuNTcon or MHC, and this year especially HAuNTcon because it's early and would give you time to digest and apply things for the coming season. This is where you'd go if you're looking to learn through great (and affordable) education and haunt tours and to be exposed to some vendors. If you're looking to go and buy stuff for the haunt, then Transworld is the way to go. By far the best tradeshow and can be good just to see what's out there, but unless you have some money to spend I think you'd be better off at one of the others. Transworld does have education that runs about $45/class, which I can't personally comment on since I've never taken a class there, but I've heard it's hit or miss.
Anyways, you can't really go wrong as you'll certainly get something out of each one, but I'd just think about what you really are looking to get out of it and choose the one that will be the best investment.
Fear Town Haunted House