Been cycling a long time. Started on my first serious road bike having 165s, the bike was a 21" (54cm). Got an additional bike a 56cm with 170s, I could tell gthe difference, the 165s felt short when I used the bike ocassionally. other bikes aquired used happen to have 170s (some shorter) My last bike, a brand new special order has 172.5s and I can't really sense the difference. Mountain bikes have longer arms in each respective frame size.
I'd wrestled with the decission whether to go with 172.5s or 175s. One seller I'd asked, right-off rec. the 170s, given my 5'10" ht.. 82.? inseam and rel. short legs (short femurs). The place I ordered the bike from told me "your choice", no recs. One member here in the forums had said one thing, very casually , " my knees go up too high" with my new 175s. That answered that.
Trends have changed; M.bikes have influenced ideas in longer lengths.
30 yrs ago bikes your size and mine; med. to med-lg., 54cm to 56cm as a matter of course came with 165s, 23" or 58cm or so with 170s etc..
20 years ago, they went-up-a -notch. Now it's over the top... trends.
Stay with what you know, besides, spinning is better (I suck at spinning)