A lot depends on what you do online. Just surfing? You won't notice a difference since regular surfing the net doesn't use much bandwidth. Netflix etc? You'll be able to watch 4K for sure with fibre, if you have a 4K display. Downloading or uploading? Definitely.
The feature that you will notice(and appreciate) right away is the upload. Fibre connections have symmetrical uploads(for most speeds). I had a bonded 50/10 connection which I got upgraded to fibre 50/50. Right away the speed became about 60/60(from the old 60/11). Backing up a phone to the google(as an example) is a thing you will see a difference(for the better) right away. The other place I saw an improvement was on optik tv. There was so much overhead that I could record a 4K channel and watch another(purely academic as there is only one real 4K channel). Never see the "all your streams are in use" message again.
As the difference between that and 150/150 was only $5, I couldn't resist the temptation and upgraded to it. While I like the fact that I have 150/150(178/178 in speedtest) I haven't had a real life occasion where I could do something that I couldn't with 50/50. But, in summary, fibre upgrade is great even at a lower speed.
In some instances the speed jump is noticeable. In my town, we went from 6Mbps service to your choice of 15 / 25 / 50/ 100 (now 150 or 250) Mbps service. Even the step to 15 Mbps was a huge jump up!