Nu am iPad Mini Retina ca sa compar, dar din ce am citit "spicuiec" cateva pentru voi:

iPad Air vs. iPad mini with Retina Display: A closer look
Battery life? Both iPads are terrific in that department. The iPad mini outlasted the Air in our standard test, but both tablets continue the iPad's tradition of excellent uptimes. You're looking at more than ten hours with fairly heavy use.
AnandTech | iPad mini with Retina Display: LTE Hotspot Battery Life
The mini managed to last 18.77 hours on a single charge, making it a bit more efficient than the iPad Air and still a formidable option as an LTE hotspot. The Air will obviously last longer, but if you prefer something a bit smaller the iPad mini with Retina Display is a great option.
AnandTech | Apple iPad mini with Retina Display: Reviewed
Our web browsing test shows a 10% improvement compared to the original iPad mini. The new mini with Retina Display can even last longer than a 4th generation iPad, and it’s hot on the heels of the iPad Air

Video playback is where we see the biggest improvement compared to the original mini. Here the new iPad mini lasts 21% longer on a single charge, once again outlasting even the iPad 4. The iPad Air doesn’t offer any appreciable gain in battery life over the Retina mini.

Our 3D battery life test is the only one where the old mini manages to beat the new Retina model. With a 1.31% margin of victory though, it’s pretty safe to say that for current 3D gaming workloads you’ll see similar battery life out of the Retina mini as the old model. This is also the only test where the iPad Air delivers better battery life on a single charge (~11%).
Tinand cont ca iPad Mini are o baterie la 3.75 V, 24.3 Whr, 6471 mAh pe cand iPad Air la 3.73 V, 32.9 WHr, 8820mAh (cifra nu este exacta totusi, e oarecum "calculata"), dupa care luam in calcul ca ambele "imping" aceiasi rezolutie dar cu diagonale diferite, mai adaugam si faptul ca iPad Mini totusi are CPU un pic mai lent... diferenta dintre cele doua ar trebui sa fie nesemnificativa (as estima undeva la 10% in favoarea iPad Air). Este si motivul pentru care Apple la ambele iPad-uri spune clar "Up to 10 hours of surfing the web on Wi-Fi, watching video - Up to 9 hours of surfing the web using cellular data network".

Datorita nebuniei legata de faptul ca productia la iPad Mini cu Retina a fost lovita de probleme mari (incepand de la ecran si terminand cu bateria), cei care aveti probleme si nu vedeti mai mult de 10 ore pe un astfel de device, va recomand sa mergeti sa-l schimbati la Apple. Sunt oameni care se plang de faptul ca au aceasta problema. E posibil ca si al tau sa fie asa DeathWings.