There are many self catering apartments in most major Sofia places and these are often better than hotels Certainly cheaper, but I recommend best place to stay in 4* or 5* hotels.
The Sheraton over the other “high-end” hotels for several reasons. First, it is a classic beauty that feels modern, but has retained the old-world feel. The business center is exceptional, except some CIA types tend to camp at the computers. Second, it is safe and centrally located. Third, the staff is excellent, not just good, but excellent. The prices are not that bad considering that anything less than $150 will get you incredibly bad service, bad security, prostitutes, and noise.
Hotel Vega is brand new and looks very good from outside. It has a good location, although it is not close to Centrum either. It is next to student’s town and there are a lot of pubs, bars and other entertainment within a walking distance. Public transport to Centrum runs at short intervals but is always crowded and not convenient to all destinations. Another advantage is that it is relatively close to the airport.
The SAS Radisson is newer and has slightly bigger rooms, but prostitutes are always handing about thanks to the several strip clubs around the area. There are few restaurants close by and the area is on the border of the city center and residential areas. The Hilton is simply too far away from the center