The Jurassic park crew supposedly had a lot of money, and I would argue that any computer nerd, at the time depicted, would have gone with that combo. SGI for Unix and the power and Macs for admin. I would have.
Pretty much. This was at the period where Macs were in an unfortunate middle ground. Still great at UI heavy stuff but not hitting the higher performance of top end machines or the low price of PC's. They still had a decent place in Office settings, education and libraries but that was about it. Of course after Windows 3 came along in 1990 the UI advantage started to erode but wasn't quiet there yet by the time this movie came along.
SGI machines mostly cost a lot of money for the 3D graphics hardware. They didn't make much sense for other purposes.
If you were already an IRIX shop, the servers were performant for a lot of uses. SGI did networking and disk I/O at least as well as Sun, IBM, and HP. We ran NFS and Perforce for hundreds of developers on SGI servers.