The better or worse on this subject is definately subjective with some people likely to prefer one over the other. I like easy, so I prefer a higher lead content than tin which makes it melt quicker, but higher tin amounts gives it more corrosion resistance. I also like the lower temps in the higher lead content versions because it keeps the heat down which makes it better for the components being soldered.
The prices you are seeing at Radio Shack probably should be ignored, IMO they've almost put themselves out of business just by not looking at their real customers and just starting to sell toys thinking that was popular. Once again marketing and bean counters doing what they do best, drive a company into the ground.
Still cost is always a part of the equation. Lead containing stuff is being frowned on and the EPA has rightfully made rules about it more restrictive. So solder being a commodity, you will see prices flucutate considerably. I'd buy whichever is cheaper taking into consideration a little bit that the higher tin contents will take a little longer to solder with. If you also prefer a higher lead content, just weight that preference with the pricing you can find and choose according to what best suits your own needs or requirements. If the prices you find are close, pick according your preference.
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