carg OK, since you asked what we think, I decided to take you up on it. My idea was based on that you selected thighbands, and the shortest possible chain too, after asking about it here. But since my assumption is wrong, I was thinking that we might be able to help you if you give us a list of pro's and con's for you for both options: that would give us an idea what is important to you in the choice, and we can perhaps tell you what we think of them, and come up with more.
I've recently gotten a longer chain actually, to 6cm now as for the options
Blouse + gymslip + tie + knee socks
+can choose what i want to wear over the gymslip
+not as expensive as the other option
-not as many layers
-not as formal as i desire
Uniform with blazer and underwear
+full uniform that i cannot escape from
+proper formal wear
+will be warm enough for all seasons so i don't have to change much at all
-Expensive
-might be a bit dull