I don't mean to be pedantic or anything (I don't really have a clue about this either), but are those valid strengths?
1. Logical progression to the conclusion (valid argument).
People like Hume and Kant deny the fact that we can apply cause and effect all the way back to the beginning of the universe. "Just because every human has a mother doesn't mean that the human race had a mother", or something.
And the cosmological argument assumes some kind of uncaused-cause in order to bring the otherwise infinite regress to a halt. But if this uncaused-cause is infinite, then is that not just as illogical as an infinite universe?
2. Principle of sufficient reason (leibniz), gives example other than infinite universe - satisfies human demand for explanation.
Does satisfying the human inclination to avoid infinity necessarily give an argument a strength? It gives an example that avoids the infinite universe, granted, but is there something inherently wrong with an infinite universe?
Furthermore, the uncaused-cause would need to be infinite also.
3. Agrees with the big bang theory (chain of cause+effect).
The big bang theory doesn't necessarily present a case for a finite universe - one might say that there have been an infinite number of big bangs and so on and so forth, which is just as bad as infinite regress.
4. Simple explanation..
Again, I'm not sure if simplicity warrants merit. The simply way to explain something is often wrong - in nature, we can neglect the effects of air resistance in calculations because it makes things simple. But that means that our predicted answer via calculation will be slightly off due to the simplification.
For the sake of an examination, at what point is a strength considered valid? Will any sort of superficial strength be worth writing down? Or is it only strengths that cannot be refuted easily. When I try to write essays about strengths of a certain argument, I tend to write down very few, as a strength that can be refuted is more of a weakness than anything else...