Check the exact model. Different RAM/storage variants can have different prices and specifications.
Check the current price. Promotions and stock changes can move prices, so use the listed price as a current reference rather than a permanent price guarantee.
Confirm warranty and seller details. A lower price is not useful if the seller cannot provide reasonable proof of purchase or warranty support.
Check the IMEI. Dial *#06# on the device and keep your receipt and purchase documentation.
Think about your actual use. A gamer should prioritize performance. Someone who spends most of the day away from a charger should prioritize battery. Someone who stores lots of videos should prioritize storage.