I think if I were in the market for a new GPS receiver today, it wouldn't matter to me if the chip is SiRFstarIII, or MTK. The tracking sensitivity of the chips is almost identical (1 dB difference). I know from reading in your other post, you are not too happy with your Deluo NavStick
. I don't think it's the SiRFstarIII chipset's fault, though. It's likely due to the smallish size of the unit - the antenna inside the Deluo NavStick must be much smaller than antennas in larger GPS receivers. A larger antenna will deliver stronger signal to the chip .
Perhaps before you buy another GPS receiver, try to use your Deluo NavStick with a USB extension cable. Place it closer to window of your van. It may work much better that way, as opposed to when plugged in directly into your laptop. It may not have good view of the sky in all directions in your current setup.