I would say just use the web updater and you can't go wrong.

Just an FYI -

I just updated a very old (certainly nor recent) , US Nuvi 200 (not a 200W) to the latest firmware 5.10 for a friend and it now works perfectly with 2 maps on SD.

sd:\garmin\gmapsupp.img
sd:\garmin\gmapsup1.img