I have a BRB 70cm and a BRB 900MHz, and an Altus Metrum Telemini (the ultra-miniature non-GPS tracker/deployment computer).
The Telemini has excellent documentation, has decent software in my experience, and is easy. It is a wonderfully transparent (you know how and why it does what it does) and functional system. However, the only time I have attempted to use it for deployment instead of direction-finding and telemetry, it fired in my hand on the pad when i powered it on, damaging my rocket (by setting off both apogee and main charges at the same time) and giving me light burns and temporary hearing damage. I still love it for easy (and insanely tiny) telemetry and direction-finding, but I will never use it again with charges hooked up. I talked to several 'old salts' at the launch i was attending, who all had negative things to say about the Altus Metrum products, although none of them had ever used them personally.
If you can get Ham, there's no reason to go with the 900MHz over the 70cm BRB. The 70cm Beeline GPS is the fastest-locking (and re-locking, after a fast boost) GPS that is currently available for hobbyists. It does not function above 135,000", however. My real problem with both the 900mhz and the 70cm is the lack of documentation or transparency-the documentation does not at all make clear what the default programming is or how the device should function, although it has functioned perfectly each time I've used it. This may be due to when i ordered mine, it seems the manufacturer was transitioning from one version to the next. That doesn't change the fact that I don't have any documentation of what model i actually have, how it should work, how I should use it, or anything-all I know is that I should wipe the flash before a flight and turn it on before the motor lights, but I don't know about how it saves data or if it's triggered or anything. If this bothers you it might be a problem.
In the end, you simply can't beat the 70cm Beeline GPS for it's time-to-lock times, however, and it has pretty decent transmit range (at least mine does-I have no idea what power it is, since the documentation isn't self-consistent), and seems to have enough memory (it recorded over two hours of data in the back of our van after recovering a rocket as we drove home, despite the documentation saying it only recorded for 20 minutes...). I'd still get the 70cm beeline.
As an aside about handsets: we're using a Yaesu of some model number I don't remember, but it has it's own GPS receiver built in-which means it receives the 70cm beeline's APRS packets, and reports the relative heading and direction to the last received packet. THat's pretty darn handy, so I think it's probably worth getting a ham receiver that can do that.
