As much as people say two pieces are the way to go, a top of the line one piece allows you to pop off the jacket and wear the suspender system so that your jacket is still with you while you get warm working drilling holes, walking etc
there is no suit warmer than a 1 piece. And if you go through the ice (which I have) you’ll be happy that your one piece isn’t allowing a single breath of that warmth out of your body.
i made the investment in a Salus odyssey suit and have never looked back.
pros - it’s the ultimate survival suit, you are effectively a super ice soldier while wearing the thing, it’s like impenetrable armour against the elements. Has pockets for everything, even spots for your picks on the exterior of your suit. (Technically for flairs while sailing) a built in winch system so someone could haul you out by your full body weight.
has an incredible suspender system in it that is more than just two buckle straps.
they actually make just the coat if you go that route.
canadian made in Waterloo, I even had a factory defect in some of the stitching near my crotch and brought it to them and they completely repaired and reinforced the area for me.
cons - it’s heavy admittedly, wearing that much armour comes at the cost of some weight. That’s what you get though with a suit that literally is impossible to get cold wearing. Ive taken that suit out in -35 in the wind and haven’t felt a single bit of cold. My hands and feet might suffer but not once have I felt cold wearing the thing.