my 2 cants:
Effective top tube length is more important than seat tube length or size, not all M are created equal. Depending on your riding, geometry would be different. Of course it can be compensated by stem length and seatpost, but better to get the right frame.
It took me almost 2 years and 5 frame to get what I want.
An example: For me, I am 1.79 also, and I ride 70% road, 10% pavement, 20% offroad.
I ride a Titus RacerX M with a 23.38 inch top tube with 90mm stem (any shorter will be twitchy for me and any longer, the bike will feel retard.) and a 0 setback seatpost. (If I use a setback, my CG will be on the rear wheel which makes it not so good to chiong, and if I reverse the setback post to set forward, CG will be set too forward, go downhill offroad will not be stable.) This is just the tip of the iceberg, 1001 factors to fit and geometry. and everybody have different hand leg and body length, different riding style. To make things more complicated, riding styles are corrected on the way and riding style may change. If most on road, I suggest you can try some L size bike. If offroad, can try M or even S. smaller frame = more nimble.