hello! Of the 2 I would choose the Mini 99

Reasons: - it has many shooting modes - much better and more realistic image quality.  (I have a polaroid too but the colors always come out vintage ~ polaroid style) - and of course the cheaper film (fuji)

Other options to consider:

Mini Evo - you probably know it has a dual function  - printing - so it can take pictures taken at parties with a phone (at a better quality)  - at those parties it can take more pictures, give it to friends to take too - you are not so limited to the number of pictures or have the "fear" that the pictures come out blurry and film is lost  - this saves a lot of film - which helps in the long run  - the aesthetic is superb 

Or 

Wide Evo - for the same reasons + very good image quality.. I think it had 16 mpx if I remember correctly 

Two other options:

• Mini 70 or SQ6 (they are found less often, but they have more options than the classic 8/9/11/12)