You can be pretty sure that there will be no violence in the subway. Only very scarce times a problem happens in any point of the network, most of those few times, fascists battering inmigrants, but it's really very very strange. you could be using metro 10 years and see none of these.
So, you can be 99,9999% sure that you will suffer no violent robbing, but you need to be well aware of pickpockets, which are among the finest in the world and are fonder on tourists. But having your luggage in front of you and cheking it after any strange happening, like somebody pushing you or something should be more than enough.
Just be aware and you can be sure that you'll have no violence or pickpocketing. Sounds a little paranoid, since almost all the people you'll find will be honest, but you have to be a bit more areful because tourists use to bring valuables and more cash on them.
Anyway, I would suggest the hybrid one because it's less time, not so much money (maybe 6 euros if few traffic), you don't have to walk ten or fifteen minutes through the subway halls with your luggage, and you´ll be safer (although it's not too dangerous)