While all of these routers are based on broadcom 53xx series chipsets, WGR614L is based on a newer BCM5354 chipset on a BCM947xx reference platform.

WGR614L runs faster than WRT54GL. Both of the router uses the Same MIPS 4k CPU architecture, but the integrated wireless in BCM5354 is different than that of BCM5352. And both of these router has same amount of flash (4MB) and SDRAM (16MB).

Netgear's WGR614L's factory firmware also supports the WPS and SES (Secure Ez Setup - Broadcom specific).

WRT54GS is a different story though. The newer versions are based on the similar chipset but the Flash and RAM is only 2 MB and 16MB. Older versions used to have 8MB flash and 32MB sdram.