Both are android box. Both by biggest DTH providers of India. One is upgraded version of older internet TV box(Airtel). Other is second chance of providing time shift tv (Tata Sky). Which one is better than other ? Lets compare one by one. From hardware to Remote to subscription to features.

Airtel Xstream+Tata Sky Binge+
ProcessorBroadcom BCM72604 B Dual-core 1.8 GHzBroadcom BCM72604 B Dual-core 1.8 GHz (ARM Cortex-A15) processor
GPUBroadcom VideoCore V HW (V3D-510)Broadcom VideoCore V HW (V3D-510)
Ram2GB1.5GB
Storage8GB8GB
PortA/V , HDMIA/V , Hdmi
AndroidAndroid TV v9.0Android TV v9.0
Recording/ Timeshift tvRecording coming soon.Timeshift TV part of binge pack extra charges
Recharge mandatoryYes min NCFYes min NCF
RemoteShortcut button for youtube, prime and netflixNo Shortcut button
Startup ScreenAndroid Home ScreenChannel No 100
Deals

Hope every relevant point was covered. If there are not elderly in the house then I would recommend Fire Tv or Mi tv instead as both are faster in reboot and easier to use with slick interface.

Fire TV Stick