From what I know of the starting models in the series they are basic utility units or so the dealer explained, my first was a 3320 then a 3520 and finally a 3720, I bought the 3720 based on advise from the dealer and the service manager, we had/have a project requiring a lot of H.P., very large bucket and pulling a dump trailer, all I know is as with all the tractors I told the dealer to make sure it was loaded.
I haven't seen a 3005, my dealer starts at the 3320 for whatever reason.