When I attended my first 10 days retreat I was amazed to see how many options there are when it comes to choosing how to position our bodies during meditation. Of course we all sit to meditate. Some people sit simply cross-legged, other use bolster and other props adopting a kneeling position, some others need regular chairs (however from what I understand they should remain straight without reclining on the back of the chair). There are a lot of variations also when it comes to the hands positioning. Some people let them rest over their knees, facing up or down. Some other people like me prefer to hold them together. While some other meditation styles like the traditional Zen schools are very specific about how and where to position the body (i. e, facing a wall in some traditions) the Goenka way of teaching Vipassana seems to allow for a certain degree of freedom.
Personally I think that every one of us has different physical needs and while sitting on the floor has a deep meaning and a rooting quality, the more important thing is to adopt a posture that we can keep without moving for a long period of time.
One hour sitting on a regular chair without moving has more value than three minutes of suffering in Lotus. But also, our body changes, sometimes we are in better shape, other days we need more support. In general it’s advisable to use the same posture all the time to reinforce the body level of comfort, but flexibility is also part of our practice.
I remember after we broke the silence on the last day of the retreat that I met a meditator who told me that he had been told for years that the “only” way to reach enlightenment was by keeping the fingers of both hands intertwined in a certain way. He only changed his mind when traveling in Asia he met a very advanced monk who had only one arm!.
Floor or chair the most important thing is to be persistent and keep on practicing!