Nice Time for me to tuck into this Discussion.
Firstly I am very familiar with the cars you have named above.
Just like You, I too have A SKODA Rapid Manual but in Diesel guise.
Then there is the fact that there is also a Jetta in our garage which dad owns & uses. So I will highlight all the distinctive difference between the two along with the cousin of Jetta & Sibling of Rapid, the SKODA Octavia.
Since you have Petrol Rapid, if you Test Drive the 1.8 TSI & 2.0 TDi engines in Jetta, Octavia, Superb you'll be thrilled by the sheer performance. These engines are just exceptional and they blend really well with well engineered chassis of these cars.
To make it simple, just like Vipul & Akash mentioned above, you can consider the SKODA Superb which feels class apart & if you are keen on another Petrol one and willing to spend extra money over Jetta/Octavia.
If You're looking for Diesel, then look at the Octavia or Jetta. Simply because you wont get your Superb Diesel until Festive Season.
Also if you consider the price difference, the gap increases even more. Apart from Richer Cabin & Extra Equipment, the Superb doesn't have any major advantages.
Now if you compare Jetta & Octavia. It's a very simple choice. If you are looking at Diesel, the Jetta is the best out there. While if you're keen on Petrol, the Octavia is a winner.
Apart from these, the difference is minor between these 2. The Octavia offers Sunroof while the Jetta comes with Fatigue Detection Warning. But one major area where Jetta scores is fhat it is equipped with Multi Link Suspension which offers superior ride and makes one feel very comfortable no matter what kind of roads you throw at it. The Octavia has to do with inferior Torsion Beam on Diesel. But the Petrol has a Multi Link Setup.
To Sum it up, The Jetta is more a No Nonsense Car with Spacious Cabin, excellent seats, elegant looks inside out, excellent ride & handling. The Octavia is more of a sporty version of the Jetta in terms of looks and the way it drives. Both are identical, but the Jetta is more comfort based while the Octavia is more Driver based especially the petrol, diesel one is par with Jetta.
So, i would advice you to TD these 3 cars and make up you're mind. If i was to buy one, it would have been the Jetta Diesel Automatic.