404 was a great hostel to stay in. If you're after a smaller hostel because you don't like the typical mega hostels of Germany then this is your place! It definitely has a homely feel about it and any help or questions we had were answered in great detail. I would easily stay there again on any future return trips to Köln!
The hostel was good. It's just a typical hostel and thankfully not one of the larger mega-hostels that are so common in Germany. Two annoying things about the hostel is that the WiFi needs a login that you need to get from reception and it can sometimes take a while to log in. Also the 'kitchen' closes at 10pm but in doing so also cuts off access to 1/2 of the communal areas so space is an issue at night if you don't want to be in your room.
Jimmy Jumps was a good place to stay. It's very centrally located to everything. The staff were super friendly and helpful when we needed help with something. The Internet and WiFi worked well and was fast. The only downside was the bathrooms/showers needed more frequent cleaning and on the day we left even though our food was bagged and labelled, our food was thrown out when the fridge was cleaned. Highly annoying as there was no warning the fridge was being cleaned!