what is your budget..if its limited,then having two keyboards with all the bells and whistles is a waste...what type of rap ,are you interested in doing? This may have bearing as far as what keyboard...of course all work fine.For R&B I would definatley go with a MOTIF ES ,Rap..I would go with the FANTOM X....If I could only have 1 it would be the fantom....
If your budget is a bit higher I recommend getting an MPC If you dont mind used I would buy everything used....some of the mpc diffenet models have different functions,and some have different sound qualities...So depending on what your needs are would determine that....I personally wouldnt use those keyboards sequncers or samplers...on paper the specs are good but lack the character often used in Hip Hop and
R@B..and I know some may come say you can tweak this and that and it aint what you have but what you put in it..sure some things can be tweaked,but certain things you cant duplicate...its really a no brainer but some are stuborn and gotta learn the hard way..
So My recomendation if budget is just a bit more but worth it,would be
1.MPC3000,4000,60,2500,2000xl..take your pick....---your sequencer,and drums,samples
2.fantomx rack--for all your strings,electric pianos,horns etc
3.studio electronics SE1 or ATC---- for basses and leads
of course when it comes to keyboards and modules, its all about what sound you are trying to get. with the set-up I listed,if...IF.IF..you have talent to make beats then you will be able to duplicate any style or sound of a producer that influences you.You wont have to worry about software issues,viruses etc..Basically power up and create.
Now I have other recomendations if you are more influenced by say..old school hip hop...priemere/pete rock