Hi Egbert, we have both, the greenhouse inside the tunnel. We are cold and windy up here so a greenhouse on its own would blow away. I would say that if you have room for a tunnel then you are better to spend your money on that. You get more room to grow and you can grow in the soil. The greenhouse is useful for raising seedlings and growing very tender plants such as chillies and peppers, aubergines and so on. All I over winter in my greenhouse is tender ornamentals from outside and some herbs. I'm not very good at winter crops in my tunnel - the last few years I have had chicks in there because it's been too cold/snowy to have them outside and they demolish everything. In Spring the tunnel doubles up for emergency lambing, with hurdles made into a pen. If on the other hand you are somewhere hot then a tunnel can easily get too hot in the summer, and you would be better with a greenhouse to raise plants early in the year to plant outside. Our equipment in the GH is homemade benches, in the tunnel, crop bars and a cold frame. I also make fleece cloches using blue water pipe for the hoops. You can invest in a drip feed system if you are rich but really neither needs much extra equipment. A polytunnel raises the temp by about 1 degree when it's cold, as does the greenhouse, coldframe, cloches etc and this is cumulative (so fleece over my greenhouse plants inside the tunnel in theory would keep plants 3 degrees warmer than outside. The tunnels best effect is to keep off the wind and heavy rain/sleet/hail/snow.