Garmin etrex 3 – best place to store maps?

I’ve been messing about with my new Garmin etrex 3 and was wondering whether there’s much of a performance benefit to storing maps on the unit’s internal memory rather than a micro-sd card.

I think that the unit itself has 2 GB memory and I’ve just bought a 16 GB card.

Is the etrex able to use the micro-sd card as an extension to its own memory (for storing tracks, way points etc.) or can that only be done on the internal memory?

Ive got the UK OS-like map on the device (etrex20) on the tech-ignorant assumption it will read it quicker/better off internal memory, and I move tracks/routes onto the micro-SD card. When you save tracks they store by default on the device memory, which fills quickly with the map taking up much of it.

I also tend to move them onto the laptop in Basecamp and take them off the unit after a while.

I would prefer to put the maps on the MicroSD card where possible. Just in case things get messed up. Especially if you are trying out a mix of maps from different sources.

Maps on the internal memory could prevent the Etrex from booting at all, or connecting to a computer. Whereas if its on the card, you can still take the card out, and use it in a separate card reader.