Pretty soon I had two Raspberry Pi 2 Model B's too, and a BeagleBone Black and a Banana Pro had also joined the ranks.
Things really got going when I bought my Raspberry Pi 3 Model B's, and I was able to compare between the various ARM SOCs, as well as the software-, hardware and community support for these boards. The absolute winner in the early days was Raspberry.
Instead of buying a third Raspberry Pi 3 Model B+ to make a nice collection, I soon had Raspberry Pi 4's. Several different models even: two 4GB Model B's, a 8GB Model B and as last purchase a 8GB CM4 (Compute Module 4), complete with 32GB eMMC and WiFi. The Pi 4's really brought me into the world of 64-bit ARM crunching, something that I had already begun with two Odroid-N2+ boards. Things accelerated when I asked Bearnol of WEP-M+2 for a 64-bit application. All of a sudden the 64-bit boards brought twice the credits, so I soon updated the OS of my Pi 3's and started looking for more 64-bit SBCs. This must have been at the time every other Tom, Dick and Harry did the same, because all of a sudden Pi 4's are more scarce than hen's teeth.
One of the stop-gap boards to consider is Radxa's Rock Pi 4, a 6-core RK3399 cruncher that is Radxa's best till they bring out the Rock 5 with its octa-core RK3588. Their later Rock 3 is more on a par with the Odroid-C4, -M1 and Banana Pi M5 - all somewhat better than the Raspberry Pi 3+, but less than the Raspberry Pi 4. The Rock Pi 4 -in its best edition- is more on the level of the Odroid-N2+, also being a hexa-core (but with the wrong combination of cores in the case of the Rock Pi 4: two performance and four efficiency). But there are more versions, and some of them may be better to avoid, as in lesser performance. I did the nasty parts in red, and the good ones in blue

BTW: I have a 4GB Rock Pi 4B+, with 32 GB eMMC...