Most wallets require you to download the code from the server (certified server). If the server is down, then you cannot access to the wallet. And if there is an unfortunate DNS attack, a compromised DNS will route the legit website to a fake IP, then you may risk losing your valuable assets. The client-side e-wallet is an application running on the client PC that holds e-coin information , and thus even if your wallet website is down, you still can access your wallet provided the node where the wallet connected to is still working.
In a nut shell, a DNS attack is hacker manage to get hold of a legit DNS and modified its IP to redirect to fake/scam website. This happens to myEtherWallet in August 2018 , and some users lost some assets. They don't know they were routed to a fake website. Using client side wallet can completely avoid this kind of DNS attack, since the wallet is run from your own computer and does not require a DNS access. However, client side wallet is still not 100% safe, there is risk from computer virus, trojan, keyboard logger etc. A better approach is to use client side wallet with keystore, this will avoid keyboard logger attack. Please do your own research before using this software!
I have developed a database to store all daily Zilliqa staking statistic beginning 30 Dec 2020, you can view the daily staked amount, number of delegators, estimated APY, and number of delegators based on the staked amount (<100k,>100k, >500k, >1m and >5m ZIL). It will available in 2 weeks.