Thanks I get the concept. But what I don't quite understand is, you would need to adjust tune your new piano anyway, so their sound would come right isn't it? Its like a new car, new bike lot of things. But wouldn't it mean, if you buy a piano that was loaned for short term like 3-5month (no idea the usage) then the sound is nicer than a brand new piano because its been tuned so many times? But that would mean you should logically get a second hand piano(under 1 yr, not 40 yrs old piano) as it would always sound better? If that's what you think, then why would we pay a brand new price on a piano has been played for 6mth-1yr? thanks :-)
A new piano isn't a car, bike, or toaster. It's made with a lot of organic materials. The wood, felt, rubber, and buckskin change with humidity and pack down with use, which necessitates adjustments in voicing and regulation to perform at their full potential. The strings stretch for the first year or two. Also, pianos are made with a lot more hand labor. With that comes variability-- no two pianos of the same make and model will sound or feel exactly the same, so the floor model isn't a guarantee of the performance of the next one.
By choosing new, you get the factory warranty and a lot more choice of makes and models...which should allow you to find exactly what you want. Less than 5 year old used, higher quality pianos are really rare in the market, and when you find them, they're often priced incorrectly for the local market (more expensive than new "street" prices). Also, piano owners who aren't enthusiasts are typically lousy about properly maintaining pianos, so even these newer used pianos are not tuned and touched up enough to achieve the desired level of stability. I will tune my current, new grand piano 6 times in the first year (because I can do it myself at an acceptable level now), and one of those visits included touch up regulation and voicing by an expert technician. With my last piano, it was tuned 4 times the first year, and then had a full day's service by a factory technician just afterward. When I'm in the field, it's not unusual for me to service less than 5 year old pianos that have only been tuned once, or never since delivery!
I'd prefer not to buy a piano that's been rented out, because of the different environments in which it has been kept, used, and the inherent risk of damage when moving pianos. However, I'd consider an ex-rental if it got me to a "tier" of piano that I couldn't otherwise afford, and really desired. During my most recent search, I was considering an ex-C&A Steinway D that belonged to a major symphony orchestra as its "house" piano. It was still a bit beyond my reach, was about 40cm too big to fit in my living room, and was voiced up for a 2,000 seat hall...and I came to my senses.