I have stayed with Urban Nomads & Hostel99 also, comparing both here:
1. Cleanliness: Hostel99 is clean & neat. It’s missing in the case of Urban Nomads.
2. Open Space: Not available with Hostel99. A nice and bigger open space is available at Urban Nomads with River view/adjacent to it.
3. Washing Machine: Hostel99 charges additional Rs. 250 for one time use, while at Urban Nomads it’s free to use.
4. Iron: Available at both places.
5. Locker: Hostel99 takes an additional Rs 200 deposit for tiny, 10 rupee lock and key. Urban Nomads does not keep any deposit.
6. Outside Food: Not allowed with Hostel99. Allowed with Urban Nomads.
7. Group Party (also with alcohol/smoking): Hostel99 will not be appropriate. Urban Nomads will be a better choice, you will enjoy it.
8. Washrooms: Hostel99 has clean washrooms, Urban Nomads not, shower is also missing in Urban Nomads.
9. Reception: Professional at Hostel99. With Urban Nomads mostly reception is missing.
10. Caretaker: At both places they are very kind and helpful.
11. Open Kitchn Access: Hostel99 kitchen is not open, you can order and get the things. Whereas in Urban Nomads you get an open Kitchen facility with all required stuff, you can cook your food.
12. Indoor Games/Extra activities: Good indoor setup is available with Hostel99 like table tennis, Carrom, Gitar, Books etc. Whereas in Urban Nomads no indoor activities.
13. Common Space: It is very clean with Hostel99, whereas not clean with Urban Nomads, still you love it as it’s open with a river view.
14. TV: Common TV is available for entertainment at Hostel99, where as it’s missing in Urban Nomads.
15. Co-working Space: Proper table chair setup is not available with Hostel99, whereas Urban Nomads has great and spacious co-working facility.
16. Location: Both place located nearby and at prime locality.

Above mentioned points are all what I experienced.
As per your need, do check-in at the most appropriate place..