You could try putting a onsie on or just a diaper so he doesnt get hot and swaddling him and then putting him in the bassinet. Babys like to feel like their be snuggled. Like their back in the womb.
He probably likes the swing better because it cradles him like if someone was holding him, making him feel more secure. My coworker had twins last year and said the only way they would sleep is in their carseats. As long as the baby is safe and there isn't anything that would block his airway I say let the little guy sleep where he's most confortable!