May be this is an old post. But I had the same question. I don't think saying "more or less all SOCs are the same" is true though. I _have_ a garmin asus M10 (Windows mobile 6.5), it is outdated, but is has the best GPS I have ever seen. I think the secret is a special AGPS-like update from garmin that is valid for 7 days. I say it is agps-like, because, I think the agps data is garmin proprietary. My understanding is, a "standard" agps data update is valid just for a few hours.
My current phone is a lenovo with an MTK chip. The general feel is, MTK chips have bad gps. But, my phone with MTK chip locks better than my friend's phone with a snapdragon. But, my phone with MTK chip is still worse than my wife's zenfone with intel atom.
Probably gps performance depends on a lot of factors like, chipset, antenna, agps technology used etc.
You should know that SOCs have their own proprietary gps data fetch technologies. MTK uses something called EPO. Snapdragon uses xtra.dat. This is not the same as standard agps. But, I think google is somehow forcing SOC vendors to deprecate their proprietary agps-like technology and use standard agps only. The standard agps server that is configured on most android phones is the google agps server BTW (that way, google can keep tabs on you
).