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.
At the time I was writing my previous post there was just one not so useful post. Now however, there are many useful ones! Including yours, so thanks.
I'm actually enrolled at the local university Aikido club and have been doing it for a couple weeks. It is a lot of fun. There is also a Judo club that is within a 20min walk from my house headed by Yeiji Inouye, 9th Dan. Unfortunately the class times are offered on the same days, with one exception, there is a friday session in Judo. I think I may try a class or two see how that goes...
For those that suggest I take up a striking art; I was in boxing during my senior year of highschool and I still feel like a competent boxer (could be wrong though!) .