Then, HolyTransaction.com is such online web multi-wallet. No Sync needed, everything via browser. So it can be accesed even on mobile. HolyTransaction supports btc, ltc, doge, dash, peercoin, blackcoin, tetherUS, Omni, Gridcoin, Ethereum. I had few issues (like failed transaction) and support always fast react even on weekends helping me out and fixing problem. Didnt heard of any missing coins (like i heard of on quoinpro for example).
For large sums I don't trust websites. Local wallets you have full control over and are the only way to go in my book.