Both printers include colour printing, USB connectivity, and borderless printing. Their most relevant distinctions are scan and copy and ISO colour print speed.
Smart Tank 520 offers print, scan, and copy, versus print on L1350. L1350 has ISO colour print speed of 6 ipm, versus 5 ipm on Smart Tank 520. L1350 supports Wi-Fi, whereas Smart Tank 520 does not. Smart Tank 520 has replacement black ink yield of 6000 pages, versus 4700 pages on L1350. Smart Tank 520 has ISO black print speed of 12 ipm, versus 11 ipm on L1350.
The choice depends on use: L1350 leads in ISO colour print speed, while Smart Tank 520 leads in scan and copy. Match those differences to your needs. Consider the first model if ISO colour print speed matters most; consider the second if scan and copy is the priority.