Tab S 8.4 LTE - Should I upgrade to Lollipop?

Hi all

Question is in the title really. Should I upgrade my Tab S 8.4 LTE to Lollipop?

I'm worried about performance issues, battery life etc, as KitKat seems fairly stable. Does Lollipop increase performance/battery life or make it worse?

I have not rooted my device as I want to be able to send it to Samsung in case of any problems under warranty.

Also, my friend has a Tab S 8.4 WiFi and he has Lollipop on it, however I find the colours/contrast are worse on his tablet then when compared to mine. I didn't notice this before when he had KitKat. Does Lollipop have more contrast etc compared to KitKat?

Lastly, if I did upgrade to Lollipop, can I easily go back to KitKat without rooting etc?

Thanks