"I'll admit" vs "I admit"

I’m confused about the two phrases in the title. They mean almost the same thing, but I have a feeling one sounds better than the other in some contexts. Can you elucidate me on the difference in meaning between them if there’s any, and when to use which? I’ll add two example sentences. Are “I’ll admit” and “I admit” interchangeable in the below?

“I admit I am no expert, but it looks to me as if he’s doing the right thing.”
“I’ll admit the offer is tempting but I think I should stick to my original plan.”

Another related question. My grammar book says “I bet” and “I’ll bet” (eg “I bet he wins the Oscar.”) can be used interchangeably in most cases. Would you say there’s no difference in meaning between the two?

thanks!
carrie

I’ll and I will, mean exactly the same thing, but both of your sentences would be said in this manner.

Thanks for your response.
I knew “I’ll” is a contraction of “I will” and was actually asking about the difference between “I’ll admit” and “I admit.” thanks!

I believe “I’ll admit” comes from “I will admit” in the sense “I am willing to admit”, where “will” is not plain future. Traditionally, the word “shall” was used with “I” and “we” to express the plain future, “will” to express an intention or willingness to do something.

“I admit” is simply a verb act: I state that I admit it; and by stating that, I actually admit it, if you understand what I mean.

“I’ll admit” expresses my willingness to admit it. However, in “I admit”, it is obvious that I am also willing to admit it; otherwise I wouldn’t do so. That is why both phrases have nearly the same meaning. I’d use them interchangeably. I’d say the same applies to “I('ll) bet”.

Perhaps you could say that “I’ll admit” sometimes expresses slightly more politeness in certain situations, and is slightly more casual in others, compared with “I admit”. I’d expect “I admit” to be a bit more frequent in books, “I’ll admit” in dialogues. But the difference is very slight.

That makes a lot of sense. Just the kind of answer I was looking for.
I really appreciate your help, Cerberus™!