I have both Fernbus and Tourist bus, both from the same developers by the looks of it. the set and buses are exactly the same. There are two addon buses namely the Neoplan skyliner and four versions of the Setra Mercedes which is the coach i prefer.
Fernbus gets boring after a while, many of the cities are exactly the same layout and do not truly reflect the the city's in the simulator, only the bus station in Hamburg is close to a true reflection of the bus station.
Tourist bus looses its appeal because of the procedures you have to go through and the compulsory tutorial. Why do i have to buy a house and then unlock shops to furnish it!! The Range Rover car is terrible to drive, some of the roads are totally unrealistic with the twists and turns that do not exist in reality. Only the airport is very close to the real thing.
So my verdict is, they both get boring, but ok to play now and again for a change.
Oh..and you do need a powerful PC to get the best out of these two simulators, I couldn't play them before i bought a new gaming PC. I run them both with all graphics settings on high. OMSI is now also running at full high settings dependent on the map, on Berlin for example I average 50 fps now.
This is only my opinion but others will have different opinions, and enjoy Fernbus and Tourist bus more than me.