For me
C2A is the one.
Free;
The ability to load the following catalogues:
SAO
USNO-A & B
Tycho-2
Hipparcos
UCAC1 thru UCAC4
Guide Star Catalogue
NOMAD
PPMXL
CMC15, plus others;
Planning and scheduling;
Drift Analysis;
Observatory Control;
Imaging tools;
ASCOM compliant
And very easy to use.
And did I mention it's free
