Advantages of multiple blogs include monetization, ease of finding advertisers, reaching right audience, and building a resource of articles all in the same niche. Disadvantages? Unless you are an expert you will run out of good articles, might have to hire writers. Multiple blogs needs more time in terms of maintenance, updates etc. It needs more resources which cost money.
You will have enough time on your hand with a single blog and you don't have to worry about all blogs that miss your constant love. Serious technical discussions happen on websites like StackOverflow anyway!
Lesser the blogs, less is the blogging burnout. Trust me, it will get you sometime or the other. You will probably sleep better at night if you have just one blog. 😬
Okay, you still want to have multiple blog, now what? If you haven't started yet or just started then think. Decide what your preferences are and go with your gut feeling. You don't want to be thinking about creating multiple blogs after having a good amount of articles already. Have a vision, it's good for you.
That is it. This isn't very detailed, I'm just posting what I think (as of now) in a very abstract way. As they say, to each his own. You might completely disagree with what you just read. In which case, I urge you to share it in the comment section below.
I hope it was useful and after the read you are in a better position to decide where to put your focus. Leave a comment if you want to know anything specific, I will try to answer.