Topo 24K: Download vs. SD Card

Greetings.

I'm once again in the middle of my love-hate relationship with Garmin topo maps. It's tough when you love the hardware, hate the software, but determine that Garmin's proprietary maps are actually the best of a bad lot for a Garmin handheld. Argh.

My fantasies this time around are two:

1. I'd love to be able to put a number of different maps on a single 64gb SD card, so I'm not always changing out cards. I seem to recall this being impossible or extremely difficult with the Garmin maps I purchased.
2. I know Basecamp is unsatisfactory in many respects, but I would like to be able to make the most satisfactory use of it possible, which includes easy ways to transfer maps, waypoints, routes, etc., to and from my Oregon 600.

Given these crazy fantasies, should I purchase the Garmin Tope 24K (Southeast) map in download or SD card format?

Thanks,
Paul