I personally like to peak all the time.  I feel it is more of a personal preference  and you should decide what you like best. 

Peak is known to be more of a formal look and seen on double breasted suits in the past.  In the recent years it has become more of a fashion look and adds a little spice to a 2 button suit with slanted pockets and even a ticket pocket and side vents.

Notch lapel has always been a go to traditional look and seen mostly with normal flap pockets on the front of the jacket and usually with a center vent in back or no vent.  Formal tuxedos are known to have this look and usually with a one button jacket and sometimes 2 buttons.

I hope this has helped someone and always enjoy sharing with you!

Much Love,

Christian