Generally, all the prime macros - whichever brand you opt for - are great lenses. Which one you decide to go for depends solely on what you choose to shoot, as has already been said.
I have the 105 Sigma, and it's a fantastic lens. If you really need the 105, you can easily buy it online for a number of stores .. even Amazon list them :thrug: ... so, decide on what you intend to shoot and then buy the ideal focal length.
If you're too new to macro, then the 105 is a "safe" bet as it'll give you better shooting distance which will allow you to shoot flowers, bugs, plants, and a whole lot more.