Ralink RT5390R as reference in Windows device manager, is the same as the RT5390. There doesn't seem to be any difference that we can tell.
MediaTek, Inc. - WLAN - Ralink RT5390 802.11b/g/n WiFi Adapter
File: 20745233_24246235429984b4390e7d1453766e4bd144db14.cab
dc87936bdef32b3d7dd114a06165241eae593cb8227b485b9d5492964a68ebb0
MediaTek (Ralink) Wireless LAN Adapter Driver
File: sp71571.exe
Ralink RT5390 Datasheet
File: RT5390_ETC.pdf
54acef50157b3be372e8b37b903a98d4d093778022864513a26f929deb31eec2