I find as far as Windows goes a 128 GB SSD for the OS drive is useless. After a year or so you start running out of space constantly. Depends how much work you do with it though. If it is just for web browsing etc. maybe it will be ok for a while. I have an older Imac that I bought second hand for $800 and I ended up putting the OS on a 256 GB external SSD. It gave it a new life and really improved performance. Have not used the IMac in a while though. Nice computer, I was impressed with the user interface, sound quality etc.I just made my purchase. I got the new MacBook Air 128gb, first day out. I could not see my self spending another $200 bucks on another 128gb when a 1 tb external drive can be had for about $50. I got $50 discount now just have to get word, so I can seamlessly transfer files. Hopefully.
My I9 with Windows 10 is rock solid and performs great with a 1 TB SSD.
Good luck with the Macbook!