Tracks take very little space so that shouldn't be an issue. Using a large memory card usually results in slower startup time when you turn the GPS on. OTOH, a corrupt map file can cause the Oregon to freeze at startup. Depending on the problem, this can be tricky to fix sometimes. If you have a corrupt map on the card, the solution is easy - just remove the card and restart the GPS.
Also, if you want to use Garmin Birdseye, those files are huge. To cover a very large area, you will probably need to place them on a big memory card. Again, this will result in slow startup time.
Personally I like to keep everything in internal memory since startup is faster. But I am not using maps from unknown sources. I used to have a 16gb card full of Birdseye imagery. It took forever to start my Montana with that card inserted, so I now only load a smaller area that fits in internal memory.