It depends what you want.
The MR0 is a direct plug and play 5 minute fit and go.
The Here you have to splice the cables for the GPS and compass.
Then "figure" a way to fit it.
Ok,
The Here was designed by the guy who designed the Pixahawk green cube and he has said he realised to get the best Ublox GPS available it would not fit into the space provided in the Solo. So the Here was born.
It also has a compass built in which being elevated, as the GPS, does not suffer from magnetic or electrical interference from the solo.
The mast is a generic folding GPS mast from eBay (8.49GBP)
The Here was 49GBP
So now you have all the info available.
Right as to the MR0 or the Here.
I have both and I would say if you prefer the aesthetics of Solo as she is (which I do) and your not proficient soldering cables drilling holes, and if still in warranty, losing your warranty, stick with the MR0 it's easily swapped back (if required) and from a rev A board you will be megga impressed.
On the other hand if you like to tinker and are happy soldering etc, and want the best GPS from Philip Rowse then go for the Here.
I intend to get 2 of my solos in the air one with the MR0 and one with the Here and record them hovering together. As such I will have a direct comparison.
But that's going to have be another day.