Best BSD Dev Board?

Hi guys. I just wanted to get your opinion on the best dev board to run FreeBSD on. I have a project I'm working on where I pretty much just need GPIO, (wired) networking, and the ability to run a Java program. My boss bought me a couple of Raspberry Pi 3Bs, but I can't seem to get anything running on it. Raspian is alright, but I'd much rather have FreeBSD or at least a BSD running on it.
So far I've tried the two experimental builds in this thread: and the FreeBSD-10.3-RELEASE-arm-armv6-RPI-B.img image I downloaded from the FTP site (which I guess is for the RP2), with the same results: rainbow screen syndrome. I've got a new serial cable, and a BeagleBone black coming in the mail Saturday. Until then I'm going to try some experiments. Let me know what you use and how it's working out for you.
Your GPIO requirement is pretty vague. Do you need analog or digital input-outputs? How many pins? Beaglebone has some unique features not found on many Arm boards. Analog Inputs, eMMC, PMIC for battery backup.

I find the lack of a Real Time Clock a hindrance to embedded use.

FreeBSD 10.3 did not support many HDMI implementations on Arm. FreeBSD11 has support for BBB HDMI.

I own the following BBB, RPi2, Hummingboard i4Pro and I have an Odroid C1.

The Hummingboard is everything I need, unfortunately many of the board features were not completed. So although it has a mPCIe slot, FreeBSD does not support it. I was messing with Atheros wifi modules on it. It also has an RTC and battery connector. The mSATA slot works so that is a bonus. They are not cheap but are more like a real computer.

Not to knock Pi as their stated goal is learning, not an embedded platform. What do you expect for $40.
The Prolific PL2303 TTY cable works good. Do not use the red wire. Rx, Tx and Ground.

Buy quality microSD cards. USB hubs can act wonky.
I see you might have the wrong image.
Raspberry Pi (1) Model B = RPI-B
Raspberry Pi 2 -Also called Model B= RPI2 Pi
The rainbow screen means HDMI not supported or wrong image. RPi2 has working HDMI.
Also on RPi2 HDMI does not initialize early, you need to use the console to see all boot messages. Only misses a second or two.
I hate to say it, but the overall picture right now is better with Linux on embedded, simply due to long term use of it on embedded, historically, and also a huge hobbyist following for the Pi using Linux (i.e. the Raspbian flavor of it). So, if you want no hassles, for either low level text-mode GPIO service, or high level usage (i.e. low-end desktop) - then run Linux.

Now, the FreeBSD development lists are boiling over with a huge number of inputs from developers working on the platform. So, if you can deal with doing some of the detail work to use FreeBSD embedded as it grows, you'll be rewarded handsomely by the experiences and involvment in the process (rather than just being a LInux embedded appliance user). That said, if you want to use one of the BSDs right now, the easiest one to use is NetBSD. It's a little ahead of the curve. My Raspberry Pi2 with NetBSD can do audio, GPIO, I2C, and a pretty functional low-end desktop running X navigation software, the latest internet browsers, etc.

I love to use FreeBSD, but I'm not a singleton fanboy. I use all of the BSDs, depending on the situation. My AMD64 almost always has FreeBSD running on it. I'm sure that in the not so distant future, FreeBSD will be on par with the others - even on embedded platforms.
Oh, I neglected the OP question entirely - which was related to what board to use.

I've had Raspberries and Odroids (Raspberry Pi, Pi2 (many), Odroid C1, C1+, and XU4). The Pi2 really is the first in the Pi line to give semi low-end desktop performance possibility, and the Odroid is faster but somewhat less supported (on non-Linux platforms). WIth the Odroid, you'll be reliant on their forums to get things going, but support there is heavily Linux/Android oriented. For the BSDs, you're on your own (although, IMO, it works fine). I'm calling the various Pi's and Odroids a tie for my favorite preferences. The XU4 is an awesome eight core unit, but no BSD for it yet.

I almost bought a BBB - because I wanted to run Minix3 on it. Phishfry is the go-to man when it comes to answering this question though :)