I had the opportunity to drive a Jensen Healey at the Carlisle Import and Kit Car nationals this past year for the first time. They are a very neat and very civilized car with nice power and the engine sounds great. There is support for these cars but they are not as easy to deal with as the Alfa but have a terrific club in the Alfa Romeo Owners Club and on the west coast in the Alfa Romeo Assocation.
I have owned all generations of the Alfa Spider except for the series 4 91-91 cars (It is the next car I am buying) and they all offer the Italian sports car experience in a affordable and pretty trouble free package. The engine has enough power and is pretty simple at the end of the day with good support for spares and also have a really good club.
The price for a nice ready to enjoy Jensen Healey is somewhere between $4,500 and $6,000 dollars. They are likely to be priced there for awhile.
The prices for the Alfa Spiders varies on the model. The series one roundtail or Duetto cars start at around $12,000 and reach a max of about $20,000. These are the ones that are already considered a inexpensive a list collector car and they are simply beautiful to look at and fun to drive. I would not be surprised if they start breaking the $30,000 barrier in the future. A driveable car that is a true iconic classic car.
The series 2 cars are the first kamm tail cars with the tail chopped off and were built from 1970-1974. They still have chrome bumpers and are quite honestly better drivers than the Duetto. The series 2 car also got an upgraded interior with a nice twin pod instrument panel and nicer seats that were available in leather. They currently run between $4,000-$6,500 and are moving up as well. A great value and almost as good looking as the Duetto. They do have Spica injection which has been known to have problems though most of those are due to user error. If you set it up once and leave it alone it works fine.
The next are what people call the Series 2A cars and these are the square tail cars with a front Rubber bumper and the same systems as the earlier series 2 cars. they are the most inexpensive of the lot with nice cars selling between $2,500 and $4,000.
There is a special model in the series 2A cars and that is the 1982 Model. This is the last of the cars before it received the rubber rear spoiler and front bumpers. It has the added benefit of having Bosch Fuel injection. This special model sells for between $3,000-$4,000 and is one of my personal favorites, especially in silver.
The next cars are the series 3 cars. These were built between 1983-1985 and are the first with the rubber rear spoilers and front bumpers. They are great drivers and still have the twin pod interior that dates back to the series 2 cars. They are also a good value selling between $3,000-$4,500.
the next are what I call the series 3A cars. They are mechanically identical to the other series 3 cars but have new seats and a new instrument cluster which is in my opinion less attractive than the earlier cars. They have a new steering wheel as well. They currently sell for anywhere from $2,000-$4,000 and are less interesting to me personally than any other spider model.
Finally there are the series 4 cars. These cars received a stunning styling update by Pininfarina, almost as beautiful as the round tail cars, more advanced fuel injection, a further upgraded interior, galvanized body, driver side airbag(I hate the way the steering wheel looks but it is easily replaceable with the non airbag better looking euro wheel) and power steering. They are very beautiful cars and are very easy to live with. A series 4 car would make a perfect first classic Italian roadster. Asking prices for the series 4 cars run the gamut from as little as $4,000 to $15,000. Nice examples are available all day for about $5,000 so don't spend 15k to try to get the best one in the world as it is not worth it.
I hope this helps. I would personally get the Alfa though I do really the the Jensen Healey, I love Italian cars.