I can provide you some direct insights into this comparison. I had two superzoom P&S: an Olympus Camedia C700 with 10 times optical zoom, and a Panasonic FZ20 with a 12 times optical zoom. I love the Panasonic FZ20, but I started to be frustrated by the average resolutions, the low light performances and the limited PP options. I add that I shoot often outdoor in any weather including foul weather and dusk and dawn when the lighting is below average.
I bought a Pentax K-7 with DA18-250mm. (The Pentax DA18-250mm is manufactured by Tamron and sold also as Tamron 18-250mm.) I skipped with kit lens. The results are beyond my expectations after a few weeks of learnng curve.
First a dSLR offers much more controls and options than a P&S.
Second the performances of a dSLR are much, much better than P&S in terms of IQ as soon as you have the right lens.
Third I got a weather resistant camera and that is a great asset when working outdoor. THe DA18-250mm is not WR but very sturdy, rock solid.
Fourth you can use a range of lenses without buying a new camera. For example, I bought a fast prime lens (Voigtlander Nokton 58mm f1.4) that is a real beauty for low light shooting. This expands drastically my capabilities and I love it. Similarly I bought an expensive full-frame lens (FA31mm) that is incredible. The lens is not cheap but its results are outstanding. That is something that a P&S will never provide.
Ultimately it may depend upon what you shoot. I shoot a lot of dynamic shots when I do not want to miss the opportunities. I do not want to miss some important shots an the dSLR is the way to go.
In summary, the Tamron 18-50mm can be highly recommended, ... especially on a Pentax
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Hope that the comments will help.