I think it's too early to say Arbitrum (ARB) is the most promising L2 project because ARB is a new altcoin and its resilience against the ups and downs of the crypto market is untested. there are still a number of L2 projects such as polygon (matic) which have proven promising and proven to be resistant to crypto market conditions, apart from that MATIC's position at cmc has also continued to rise.
You mixing blockchain and coin into a pile, which you shouldn't do. The ARB coin is indeed new, but the mainnet Arbitrum was launched in 2021 and during this time has established itself as a convenient platform for launching smart contracts that are compatible with Ethereum. Accordingly, the value of the ARB coin will not affect the reliability of the Arbitrum blockchain in any way.