To be honest, neither is better. Don't want to be rude, but a betta NEEDS a bigger tank than that, with a heater.
Snails poop ALOT, and will quickly fill up your tank with deadly ammonia.
Shrimp get eaten.
2.5 gallons is not giant. It is suitable.
I am glad your betta lived a long life, but was he truly happy?
That is like saying "well a human can survive in a closet". Would that human be happy? NO.
but, if you want your betta to be cramped,cold, and unhappy, then that is your choice, not mine. Snails and shrimp like rectangular tanks because it gives them more room to swim, and escape predators, like Bettas.
I am Truly sorry if i upset you, i am just worried about your little guy.