Another note- the Minolta Auto-Meter is most certainly an incident meter. It becomes a reflected or spot meter with adding accessories or changing out the incident dome.

As to metering using your Canon dSLR, you may be lucky and getting good results that way, but in my experience, digital camera meters are calibrated for digital sensors, and ISO 100 does not mean the same thing as ISO 100 for film. What it means is 1/2 the sensitivity of the ISO 200 setting. I have two meters - a Minolta Spotmeter-F and a Sekonic 408. Both of them agree to within 1/4 stop, perhaps even closer. My film exposures with them are dead on. I have yet to find a dSLR sensor that matches them. Most dSLR exposures I've found are way overexposed if you go with the handheld meter reading (I've observed this with studio strobes - I don't really have call to use the handheld meter when shooting digital in natural light or with TTL flash). And frankly I'd rather carry a handheld meter than a second camera system to serve as just a meter.

If I were going to keep one of those meters, I'd keep the Minolta because it has the spot attachment and because should you ever want it, there are additional accessories for it (at one point they made a probe you could use to spot meter off the ground glass of a view camera, IIRC). I don't know about the Gossen, but the Minolta definitely can meter flash exposures and ambient/flash combination. That's something that none of your dSLRs can do for you. So should you ever want to shoot an interior and balance the lighting with off-camera non-TTL flash, the Minolta will be extremely helpful.