New Yamaha C109, C113T vs. 25~30 years old Used U1 vs. digital piano

[hye128]

It is very interesting to read the articles posted in the forum. There are really lots of knowledgeable people here. I wish any of you can help me to figure out whether I should buy a new Yamaha C109, C113T, a 25~30 years old Used U1 or a digital piano or any other piano in my budget range.

I am looking for a piano for my daughters. They have studied piano for almost 2 years. They are using a keyboard currently.  My budget is around CAD3,000(US$2,500) to 4,000.

I was looking for a used Yamaha or Kawai piano after reading a lot from the internet. However, my budget can only afford approximately a 30 years old reconditioned U1 from Piano stores or 25 years old from private sale.  When I was looking for a used U1 in a store recently, the sales rep tried to pursue me to buy a Yamaha C109 or C113T. They are in a price of CAD3700 and CAD4700. Interestingly, when I was checking the old U1, a person in the store suggested me to buy a digital piano. I got confused of what to buy.

The pros and cons can be as following:
Old Used U1:
(+)A good used U1 will have better songs and can last until my daughters complete all their piano studies. If they drop after some years, I can still sell it for a reasonable good price. 
(-) The risk is high to buy a used piano. If I buy a bad one, there will be a lot of pain. It is time consuming to find one too.

New C109, C113T:
(+) A new piano will have lower risk.  It is easy to get.
(-) These 2 types of piano are under 45'. The sound may be worse. If my daughters will continue to study, I may need to change the piano to a better one. A new piano will depreciate more than an old one.

Digital Piano:
(+) I was told the sound of the current digital piano is as good as an acoustic one. The touch and every thing are the same. The price is much less. It can be used more creatively.
(-) I don't know anything about digital piano. If my daughters play digital piano, it could be hard for them to play an acoustic one later. The depreciation is big.

Any comments will be very much appreciated.

Thanks,

hye128