Moto has a lock on the radio strength, but hate's users or rather, hates consumer warranties so they lock the crap out of their phones to prevent tampering.
Samsung has never prevented the community from playing and infact
has given early access to code for developers to assist with a bug they created,
and donated 4 development phones to the CM guys to guarantee CM support for GS2, but radios are the pits and recently it seems
they've been tracking rooted devices. The root tracking is no biggie to me, but I'll let you off the hook willingly if you ask instead of secretly track. Or instead do something like watermark if rooted ( a la N1) or something but integrating tracking into the device is a bit much IMHO.
HTC has been ok with their unlocked bootloader program, but given their storied history with QC issues (to be expected when they make so many phones), do you really want to let them off the hook on the warranty when your phone could stop charging tomorrow due to a build issue? Happened to my EVO 6 months into owning it, was a common issue and listed on the "known issues", and no ROM has ever caused a micro USB cage to loosen so it's not a result of modding my phone.
LG ... well they make a decent phone and have been good to the mod community (see Optimus S/M/V/etc), but their lack of ground breaking device or flagship devices has limited adoption to mainly that line of devices.
Hopefully future devices will be better received because i REALLY loved my Optimus, best phone I've ever developed for. It's lack of specs were overshadowed by it's friendliness to the mod/hacking community.
Sony has done great things for the community including heavily contributing to googles source allowing for quicker updates to their devices,
and support for the mod community, but their limited US market penetration has been a draw back and the US devices certainly aren't groundbreaking or flagship phones.
As you can see every OEM has ups and downs. Most importantly is what matters to you. If carrier signal is a concern then maybe avoid Samsung or find a carrier that might offer a better solution for you. If a moto phone is having signal issues, it might be time to face the music and shop providers.