Going for features over ease of use, Netop's Remote Control is the most complete of the bunch.
It's aimed at businesses, but the reasonably priced Pro version includes everything that you need to get it running on a host and guest PC.
You'll need to have some technical knowledge simply to install the software, but it's still not quite as fiddly as some software we've seen.
It's the sheer amount of options here that really impresses. Installing enables you to access and edit Registry files, perform inventories of hardware and software on remote systems and even access PCs before they've loaded their operating system. It works incredibly efficiently and gave us the fastest file transfer time.
The price includes one host and one guest installation, as well as unlimited upgrades in the future, although Netop will do bespoke prices for multiple licences.
If you can get past the slight clunkiness of the software, Netop Remote Control is an all-round winner.