First of all, congrats on getting a bike! There is not much I can add to the above advice but I'll try. Both bikes are good so you can't really go wrong. The key difference is the brakes. The V-brakes on the 2000 model are Avid's lower end models but they will still be very good brakes. The biggest advantage to discs is in wet conditions, however and since you are going to be riding in wet and snowy conditions you might want to consider this.

As was pointed out above, upgrading to discs later on can be more expensive then going for it now. If the hubs are not disc-type then you can't mount a disc rotor and you will have to buy new wheels ($$) or have the current ones rebuilt on disc hubs (also $$). And the frame and forks have to have disc tabs. The Avid disk brakes get great reviews. Perhaps Spic-Mick can comment; I know he bought a set a few months ago.

The difference in the brake levers is not huge. The speed dial is an adjustment on the levers to control the lever pull/cable pull ratio. But the SD in SD-1.9L also refers to speed dial so the 2000 model also has this feature.

As for the "threadless", this refers to the headset/fork/stem junction. I agree with riderx, I am 99% sure that both bikes are threadless. The most obvious visual difference is in the stems: Threaded stems fit inside the fork and threadless fit aroundthe top of the fork. I will try and find some examples for you.