Dieter: Either this is no beginner stuff or I am a beginner at it, in any of which cases I allow myself to have a go at it. I'll consider the two circled points to be points (P) already.
I think this is the best move. It makes 2 P with a local tally (T) of 1. Next a is 1,5 P with a T of 2. So the miai value seems to be 2,75
On the other hand, this move makes 0 P with 1 T. Next, a is 3,5 P with 2 T, for b is White's sente. So the miai value here is 1,75
is 1P in 0 T (= in sente). Next, B makes 1P and makes another 1P in gote at a. So this is actually -0,5 in sente.