Interested in Q7 s-line. 2014 vs 2015
 

I'm looking for a nice and reliable 7 sitter SUV. My wife wanted to try Audi and the Q7 caught her eye. Is there a main difference between the 2014 vs 2015 model? Are there major issues that people are aware of? Are there any "must have" packages to look for? Thank you so much!

Also, is the s-line worth it compared to premium plus? Is it the same engine and transmission just with different tune?

No difference between years, just the packages offered.
Prestige has higher HP in TFSI, none in TDI that I know of, either way, all can be tuned to increase HP.
S line adds 4 zone climate control and 4 seat heat. You can google the brochures for both years. That is what I did. I looked between 2013 and 2015, but I liked mine is still in warranty for a couple hundred more miles.
There are tons of packages (options) for the Q, Sport package is most desirable (Euro V12 Look), you will know when you see it, they look awesome.
Air suspension!!!!!!!

I opted for 2015 Prestige S line with air suspension and tow package, these were a must for me. I don't think I would own another vehicle without air suspension.
I am discovering other options like ACC Adaptive cruise control that might have been nice.
I love mine, no issues so far, excepting gas door not locking with car which was a hassle free warranty issue replacement.

I hope this helps!

I do have both and they are both great! I just don't know where I'm going next. I don't like the new Q7. To me it looks more like a station wagon on steroids. Does not feel like an SUV. Very delicate. My vehicles are solid!

2015 Adaptive cruise was no longer available. Except I think the rare S-Line Sport Style package. It is a great feature but can be hard to find. Other than that the two years are nearly identical.

As far as needed features - If you tow, I highly recommend air suspension. Get one with the 4-zone climate control if you plan on regularly using the third row. It is an option on Plus models and standard on Prestige.

S-Line has more value for Gas over a TDI. It is mostly an appearance package on TDI, with the only added functionality of headlight washers. Also S-Line is only available on Prestige models, so comparing it to a Plus means you get the added features from Prestige (4-Zone,F/R corner cameras, Adaptive Lights, etc), so depending on what you want it is can be worth the bit of added cost. Depends on you and the features you are looking for.

The 2015 Q7 was the last year before the model upgrade. It is not the first model upgrade year.

Having owned both a 2010 and a 2015 Q7, I can assure you that there was a big improvement in the technology of the 2015 over the 2010. I'll bet the 2015 is even more advanced than the 2007.

I am very pleased to have the 2015 instead of a newer model.

I'll admit, it is a little depressive that there are other vehicles with nicer, touch screen Tech and features, but, I am Just saying, there is nothing out there that can give you great towing capacity and power and air suspension!
I researched everything, of course, Cayanne, Toureg, Mercedes can do these, but they don't look like the Q7!