Short answer — for most people looking for “everyday banking” in Sri Lanka, Commercial Bank of Ceylon (ComBank) is the best overall private-bank choice; Hatton National Bank (HNB) is the best alternative if you prioritise a highly rated mobile app and multilingual support, and Sampath Bank is a solid runner‑up for retail convenience and payments.

Why (quick comparison):

• Commercial Bank of Ceylon — best overall for everyday use: largest private‑sector branch/ATM footprint, strong retail product range and national presence (helps with cash withdrawals, deposits, branch services and merchant acceptance). It’s also repeatedly recognised in industry awards as a leading bank in Sri Lanka. (en.wikipedia.org)
• Hatton National Bank (HNB) — best for digital/mobile and accessibility: HNB has a widely used, highly rated mobile app (recently launched trilingual support) and a large network of branches/ATMs — a good choice if you want excellent app features and Sinhala/Tamil/English support. (Some app reviews show mostly positive ratings but occasional complaints — normal to see mixed reviews for any busy digital service.) (hnb.net)
• Sampath Bank — strong retail orientation and reliable day‑to‑day services; often recommended for payments and youth/student products (good alternative if you live/work near its branches). Recent sector reporting lists Sampath among the top private banks. (srilankabiz.lk)

Other things to consider for everyday banking (check before you switch):

• Branch/ATM proximity to your home/work (most important in practice).
• Mobile app features and stability (bill pay, transfers, mobile deposits).
• Monthly/transaction fees, debit card charges, and ATM withdrawal charges.
• Customer service hours, local language support, and POS/merchant acceptance where you shop.

If you want, tell me which city or neighbourhood in Sri Lanka you’ll be using the bank in (or whether you care most about branches, ATMs, or mobile banking) and I’ll compare the three banks’ local branch/ATM coverage, app features and typical fees for everyday use.