All of the Rotoms share the same base stats except the normal one which has lower stats in both forms of defence and attack, though the HP stays the same as the rest and it has a slightly higher Speed stat.
Of course, each Rotom has the Electric type and another type which has something to do with its form. That type determines are great amount of the Rotom's capability and wheter or not it suits you. Check this for the information and compare each form's type pros and cons.
Also, since the stats are the same (with an exception of the normal one), attacking and defending also comes down to the form's movepool (the moves it can learn). This will display information on each of the forms (alternate using the tabs above each section marked with the name of a forms) for any further info, including their learnable moves.
Hope this helps... :D
