My thoughts...
Hi there!
I'm an RSA for a Harris phase 2 system and on the admin board for a moto phase 1 system. I'll share a few thoughts that might help.
1. It's been said and is true that moto radios will work on the phase 2 in all of the required P25 compliant areas. OTAP is not one of those so there must be some proprietary servers to bridge the gap. Not too hard really, just expensive and one more link in the chain to fail.
2. Phase 1 radios will work, but it will revert the talkgroup (and voice channel) to fdma, rather than tdma.
3. I use the Harris XG-75, XG-25, and XG15 on my system for all portable users. The higher model number represents a higher tier and lower represents the lower tier. They are not bad radios. They don't hold up as well as the moto or kenwood (though that may be my users as opposed to the manufacturer).
4. we have a few of the xl-200p in all band and LTE. very nice radio and I like it far better than the APX.
5. We use the xg 25 and xg100 mobiles. Very solid radios and feature packed.
There is not a ton of info on Harris out there as they do not hold the secondary market in the same way that Moto and Kenwood do. They have also been sold a myriad of times so their name changes. They are also quite expensive as well. I use Harris (ma/com) m7100 as my mobile ham rig daily alongside my d710. Really great radios.
I hope my ramblings shed some light for you!
73's
KJ4NFP