The L6370 and Smart Tank 520 share printing, scanning and copying, USB, borderless printing. Their confirmed differences are set out below. These shared entries establish a common baseline and do not, by themselves, favour either model. The specific differences below can guide your choice by need.
L6370 supports an automatic document feeder; Smart Tank 520 explicitly does not; L6370 supports automatic duplex printing; Smart Tank 520 explicitly does not; L6370 supports automatic duplex scanning; Smart Tank 520 explicitly does not; Replacement colour ink yield is listed at 8000 versus 6500 pages for Smart Tank 520 and L6370; Rear-feed capacity is 100 versus 0 sheets for Smart Tank 520 and L6370.
The L6370 may suit a need for feeding multiple pages for scanning, while the Smart Tank 520 may suit someone prioritising higher stated replacement-colour yield. Consider the actual functions, throughput, and paper format required. An entry supplied for just one model is insufficient to conclude that the other lacks the feature.