If you ever wanted to know what walking on eggshells sounded like in a poem, this sonnet is a prime example. The speaker buries the climax of the first part of the poem – the question of whether God demands "day-labour, light denied" – inside all these other delicate expressions of why light is so important to him. The poem has a lot of short phrases separated by commas and which seemingly bring us further and further from the point, as if Milton is worried that the whole sonnet might crack open into a steaming mass of resentment. It's like if you had a classmate who said, "When I think about how my pencil just broke, I can't finish my math problem, and I like math so much, but you really need an eraser to do it, or else you might be stuck with a wrong answer, which would lead to a bad grade; 'Can I borrow a pencil?' I would want to ask you." Just ask for the darned pencil already!
However, when we consider that the speaker is about to talk to God, we can understand his desire to be cautious. The decision to questioning God's judgment is not to be taken lightly. The speaker is so cautious that he says, "I fondly ask" after he asks the question, which serves to take the sting of arrogance and insubordination out of it. Put another way, the time it takes you as reader to figure out what the speaker is trying to get across lessens the direct force of his statements.
"Patience," by contrast, is more direct. It uses shorter, more declarative sentences like, "His state is kingly." Because they are making complex arguments, both the speaker and "patience" use frequent enjambment, where one lines carries over into the next without a pause. This gives the poem a prose-like and slightly evasive sound (the eggshell thing, again). The entire poem builds to the final line, which does not carry over from the previous line and sounds remarkably clear and straightforward: "They also serve who only stand and wait." And we breathe a sigh of relief that the speaker has managed to hold things together until the end.