Seriously, would most agree having a judo background is helpful or unnecessary? Nearly 50 views and no useful replies...I would really like to hear from someone who has experience doing both Judo and Aikido.
It's an odd question, which may explain why you're not seeing answers that you judge as "useful". If you'd asked, "I'm trying to decide between judo and aikido, can you help me decide?", I'm sure we could provide some helpful information. Likewise, if you'd said, "I already have a judo background, will this help me in aikido?" I'm sure you'd get some good answers there. But you have no background in either, and want to know if a judo background is either helpful or unnecessary to studying aikido (which is a bit of a false dichotomy, but let that go for now). I'd say it can be helpful, and that it's not necessary, but that that doesn't have much to do with your situation. If you want to know whether studying judo for four years and then studying aikido for four years will somehow have you further along the aikido path than just studying aikido for eight years, I'd say of course not, and why would you think it would? As the saying goes, "If you don't know where you're going, any road will do." There's no point in asking which road to take unless you also consider where you want to end up.