I'll explain it as I see it. On my last A3 I had the Tech Pack, the only bit of this I really used was the sat nav. The display size is great as is the resolution, I only got it because I bought a car from stock which already had it fitted. Originally I was told that it just had SD card nav, but the salesman had made a mistake. So I got it for an absolute steal. Would I have paid the full price, not on your life. So when I specced my S3 I went for the SD card sat nav. Obviously some aspects are not as good as the Tech Pack but it's more than adequate. The reason I went for a built in sat nav is convenience, I already have a high spec unit I use on my motorbike, but I find it all a bit of a fuss putting it in the car, taking it out of the car when I park, including rubbing the tell tale ring on the inside of the screen off. A good friend of mine, who is a keen rambler, was parked up, his was the only car with a ring on the screen, when he came back the passenger window was broken, glove box open and sat nav gone. His was the only car damaged.
So I would strongly recommend the SD card nav. I do appreciate that many younger people are well into their tech but much of it is well beyond me. If I want access to the net then I'll do it on my phone when I'm parked. But this is only my opinion, other opinions are available.
Hope this helps?