FFPCogs

Without fail
Absolutely. Actually entering a basement through a Bilco or other entrance door is preferable if it can be accomplished in a timley manner thus allowing the initial first floor interior line to be used to prevent fire spread up the stairwell.
Textbooks and class curriculums are wonderful tools but rarely encompass the realities of the fireground or the variables thereof. And while it may not be an accepted pratice in your area, the tactic of facing forward while going down into a basement is a sound one. Not only because you are facing the fire and therefore better able to judge the conditions, but also you maintain control of the line and have it available for immediate use in the direction you will need it should it become necessary. If the situation warrants and you need to be on your keester your feet will be in front of you feeling for the the steps and any weakness of them as you descend. Also having the line forward and at the ready allows you to hit any fire threatening the stairwell thus protecting it (and you) while helping your decent to the bottom of the stairs. As with any other evolution training and experience are the keys to success.
Never enter a fire area without a charged line and for basement fires have a control man at the top of the stairs to feed the line down whenever possible. And regardless of which direction you choose to face while descending, speed is of the essence...the last place you want to get hung up is on the stairs. All the heat, smoke and gasses are going to be headed right up that path of least resistance and becoming more and more severe for you, your fellow FFs and any victims with each passing minute