Re: Aikido against judo
Here is an observation for personal and second hand experience.
A well trained Aikidoist can go and cross-train in a Judo dojo and find that much of what he has learned is directly applicable.
The period of adjustment can vary depending on how they trained in Aikido and other personal factors but there will be one. The reason is you are playing a different game vis a vis the preferred combative distance. Still, the learning curve should be far steeper than a complete novice.
If you play the Judo game (and you should since it is their dojo) they have the advantage. If they play yours you should have the advantage. That's what experimentation and research is all about.
I have my personal example but a really good one is Kieran Felton who won gold at under--90kg level in the kyu grade competition in the British Nationals. Less than a year before he had not done any Judo just Shodokan Aikido. The guy has talent but his Aikido training didn't hurt him in the least.