I've been using Amigas sinse 1988. To this day, I love the philosophy behind the design of the OS, and the hardware too.
A year ago I began collecting vintage Macs, LC III, Quadra 800, G3 server (biege tower running OS9). The LC & Quadra had hw comparible to the A1200, A3000, and A4000. I run Mac OS 7.5.5 (now freeware) on them which came out in the mid 90s. After a year of living with 7.5.5 and trying to make it work, I can make some suggestions for comparison. First, find a Mac that compares to a specific Amiga model that you're interested in. Then, try finding software on the net (MacOS, games, applications, diagnostics, etc). Make sure all of these elements are compatible. If things go wrong, take stock of the features built into MacOS for diagnostics; pay attention to the clarity of the error messages. If an installation goes wrong, how many work arounds are there? Check out the utilities on the net to help you through. Try to get your vintage Mac on the internet. Who can give expert advise? Run modern multimedia files (mov, avi, mpeg, mp3s, mods, etc). Can you find meaningful and useful content?
The machine outlined in my signature is still my main machine for everything. Other machines (OS9, Windows XP) sometimes suppliment it's abilities. I wouldn't choose to do this with any other vintage machine.