well, Losing a game as alien is actually NEVER EVER fun. I have yet to remember a time when losing as Alien was even SLIGHTLY fun and not frustrating and angering.
And I know why its so angering. Because Losing on Alien is heartbreaking because you put in all that time and effort into dropping RT's chambers, hives, etc. Getting your team in order, finding out who's doing what and going what. and then.....
All of that just to have your hive Killed by a few Shotgunners, Or to sit and try to break the inpenitratible walls of a well defended Seige Base.
Its like building a wonderful sand castle only for it to be owned by a giant title wave, Or fat kid missing a diving football catch and landing straight into it.
But on Marines, you simply just take the weapons, hold E for 15-50 seconds to get some buildings up and follow your waypoints. If you get pushed back who cares? Last stands are quite fun for Marines.