Re: aikido Vs ju jitsu
Aikido sort of is Jujutsu. Brazilian Jiu Jitsu is a specific kind of Jujutsu. Aikido has its merits and so does Brazilian Jiu Jitsu. Study either and you will learn a lot.
Don't worry about what is practical or not for now. You don't have enough experience to understand what is or is not practical, if you did you wouldn't need to ask this question. Spend some time with either system, then you can start to ask these kinds of questions.
For now trust that the inventors of both systems know much much more about martial arts then you. Learn their systems and try to understand them.