Hi,
I have owned both the rigid and DR summicrons. I noticed no difference between the two lenses on colour or B+W film. My 2 pennies CDN. 🙂 Based on your budget, I would recommend a faster f1,4/5 lens for greater low light versatility. The two lenses I'd choose between would be the ZM C Sonnar 50/1,5 or a type 2 Summilux 50/1,4 pre-ASPH. The v3, which has a slip hood and close focuses to .7m, is not within your budget, but it is optically identical to the v2 which has an external hood and a close focus of 1m. Bear in mind the ZM 50/1,5 close focuses to ,9m.
Buying older vintage lenses is a bit of a dice roll. You need to be ultra-cautious and wait. I have found that by the time I had bought the DR lens, its hood, and then its goggles, that I had spent a fair chunk; so try to get them altogether. However that's not always possible. So very often you can end up spending almost as much on a vintage kit as on a modern lens kit, especially if you want your lenses to be in excellent condition, as you should as Tom A states.