I don't think that you can compare it so easily. The deck department had only about 66 people while the engine department 325 and the victualling department 500. Also the crew members of the deck department had been on the boat deck helping to load and lower the boats and had been placed in those boats. The victualling department, depends on where they were. The A-la-carte crew were keep below, the stewards were either helping passengers or at the boats etc.
The engine department was mainly below deck in the different boiler rooms and send up on deck at different stages of the sinking. Many of the 8 - 12 watch was still below and released at about 1.20 or 1.40 a.m. Then there was also the fact that the officers at the boats on the port side did not allow many of them into the boats. Lightoller for example only allowed about 2 crew members into the boats and in some of them there were 4 (in case of No. 16 even 6) while the boats on the starboard side took more crew members on board. Many stewards left the ship with Nos. 11, 13 and 15.
In the lifeboats the passengers, especially women and children, had priority. Crew members were included AS crew members, to handle the boats and to manage them. Obviously the seamen were most in demand in that respect, and manning the lifeboats in an emergency was part of their job. The shipping regulations demanded that seamen were placed in every boat, and with just a couple of them in each one a high survival rate for the deck crew is guaranteed. Not all survived, of course, because the boats needed to be lowered as well as manned by seamen, and those who lowered the last ones couldn't also be in them. If additional crew members were required for muscle power - to row, for instance - it was a question of being big enough, of being in the right place at the right time and of stepping forward before anyone else. So a heftily-built fireman had a better chance than a 14-year old bellboy.