The portal is great. No matter how useless it is, it's a stargate portal that will make any future newcomer envious, can be perfect in a Frink area, and looks very good in the place you chose for it. Took me zero seconds to buy that awesome portal and the ghost zapper, which I consider equally awesome (visually). Also it's limited, you can always get Mel and the Aztec later if you get lucky with some scratchers, this will be gone at least until next halloween (or less likely yard sale).
After that I'd choose the Aztec over Mel, but I'm more of a "buildings" person (neighbors tend to notice buildings before characters when visiting your town) and the Aztec's design is one of the best in the game. It's probably one of the best looking non-limited buildings imho, along with happy sumo, but much more iconic than happy sumo. For these same reasons I have the Aztec in my town but not Mel (yet). Also, get the portal.
