As I have always told my children, "want" and "need" are two entirely different things.
What I can also tell you from being around people with cutters for at least 10 years is that I have seen people who started out with a smaller cutter, wish or decide to upgrade to a bigger cutter. I have never seen anyone want to go down to a smaller cutter.
With that said - my main advise to anyone trying to decide is get the biggest cutter that your space and your budget allows for. I have used cutters that use only a regular size (8 1/2 x 11) size piece of paper up to my 18" SB. My SB is my favorite and go to machine even though I still have others I could use.
As far as sacrificing "precision" - a smaller cutter is not necessarily a better cutter for "precision". I have owned much smaller cutters then my SB, and they were not as good as my larger SB. As far as a smaller SB and a larger SB, I think you would find that they both cut the same. They use the same blades, same settings, etc. As far as being cumbersome to cut small projects on a larger cutter - no, it is not. If you are planning on cutting a lot of small pieces/parts - you can lay them all out on the mat and cut them at one time with a larger machine as opposed to having to switch in and out more with mats in a smaller machine. Just depends on what/how many you are cutting at the time.
To give you the best advice/information as to whether a SB of any size is right for you - the important thing you need to tell is what you want to cut - you indicate "sharp intricate cuts" - but what do you mean by that? You indicate that you thought you would have to get a laser cutter to get what size/intricacies that you want - but a laser will often burn paper/cardstock. If you have any questions about the items you want to cut/ the media you want to use - it is always best to talk directly to Sherri and share with her samples so that she can tell you for sure if something will work or not. I have seen a few people "assume" and get disappointed which wouldn't happen if they reached out directly to the seller and have them do tests cuts and/or discuss in detail what they are expecting from the machine.
Finally, yes, there is a learning curve but if you take your time, use the learning center and work slowly through simple projects to more complicated I think you will find that it is easy enough to master. Most people struggle when they want to jump right in and start with a hard project then get frustrated and disappointed when they can't get it to work correctly the first time.