Whats the difference between btc wallet and btc wallet with segwit?

btc wallet (Legacy) using addresses of the form "1" while segwit wallets using addresses of the form "3 or bc1"
lower transaction fee and fast confirmed

Not every address starting with a 3 is segwit nested P2SH.
Multi-signature addresses start with 3. They already were used 5 years ago.
Native segwit addresses use the bech32 format (starting with bc1).

With removing redundant data from the transaction, segwit reduces the size and therefore the overall fee of the transaction (no influence on feerate [sat/B])
Transactions do not confirm faster with segwit. The speed on confirmation depends on the speed at which blocks are found (on average: 6 per hour)