The definition of good handling is subjective and personal, so one person’s preferences are as good as another's. But it’s important to recognize that there is a spectrum of opinion, and not everyone accepts the “bigger is better” approach to tires for Alfas. Also, there are a couple of technical problems with fitting large tires that should be pointed out.
In the 70s, the stock tires for 105/115 series Alfas were 165/80-14s. I made a long search for tires in this size and learned that they are essentially unavailable in the US now. Coker tire in Tennessee has Michelin XZXs in the proper size for about $100, and has been saying for six months that they will eventually have XAS, too. I like the way the GTV handled with the XASs, which were a factory tire for it, but did not wait to wait for them or pay the price Coker is asking ($155 each).
Nowadays, 185/70-14 seems to have become the new default size for original equipment-type tires for 105/115 Alfas. I believe this was also the size originally fitted to later spiders at the factory. The overall diameter is the same as stock, and they fit on the standard 5.5"-wide wheels of earlier cars, as well as on the 6" wheels of late spiders. Quite a few manufacturers make tires in this size, so there are a number of choices and price options. However, they tend to be garden-variety passenger car stuff. Performance tires have moved on to lower aspect ratios.
The next larger tire that preserves the stock rolling diameter is 195/65-14. These will still fit on 5.5" or 6" wheels without problems. Unfortunately, there aren’t many choices in this size. I’m using 195/65-14 Yokohama AVS intermediates on my GTV. They are wider than I had wanted initially, but they are excellent tires, and I have not seen any adverse effects of the 30mm of added width relative to stock. Dunlop D60s are also available in the 195/65-14 size.
Some people have resorted to 195/60-14, a size which offers many more choices in performance tires. One tire that gives excellent performance for the money is the Yokohama A509. However, be aware that this size does reduce rolling diameter substantially, which will throw off the speedometer and odometer, and change ride height. It also changes appearance, if that’s important. Going up to 205/60-14 the diameter is about 3/4" less than stock, and on an unmodified street car with 5.5" wheels, sidewall flex and clearance are real concerns (spacers are required behind the rear wheels for clearance with the bodywork). Personally, I would not use such a wide tire on a stock, street-driven spider.
In a street car, the usual approach is to preserve the original diameter of the tire/wheel combination so the gear ratios and ride height are maintained and the speedometer remains accurate.
With 195/70-14 tires the overall diameter would be about 0.50" larger than stock, with 195/60-14s, it would be about 0.75" less, and with 195/50-15s 1.2" less.
Fitting a tire that increases overall diameter effectively makes the final drive ratio longer, while reducing the diameter makes the ratio shorter. A sequence of tires sizes that more or less preserves the original diameter is:
These are the only sizes I would consider, unless I had well defined reasons that dictated doing something else.
Perhaps by modern standards, the tires originally fitted to the 60s and 70s cars were too small. But by the standards in effect when these cars were built, something close to the original tire size would provide the “correct” handling. Evolving technology has changed not only the behavior of cars at speed and the techniques used to drive them (when was the last time you saw a four-wheel drift in an F1 race?), but also our perceptions of what is good. Big, sticky tires that stay planted to the road may be faster on the track, but on the street, less capable tires that run at greater slip angles can give a lot of fun at much lower speeds. If you want a classic driving experience to go with your classic Alfa, the original size tires are the ones to use.