The bigger the better but then cost comes in to play. Just going from the 10 foot TEK mesh to a 12 foot TEK mesh is a big jump in money (about $1000 difference). Finding a used 12 footer in decent condition (and nearby) is very difficult to come by. And the larger the antenna the tighter the beamwidth which makes it difficult to align the dish. I don't want to have to go back to doing alignments like I did back in my 6 meter Ku band days. Too bad so many people abandoned ship and went to the pizza dish services or cable.Most dish size charts provide the minimum size based of a full transponder at average modulation, power and FEC.
Narrow bandwidth, more aggressive modulations, high FEC and lower link budget calculations require larger and higher efficiency reflectors. Rejection of adjacent and terrestrial interference also increases the target transponder's CNR.
If a portion of the C-band spectrum.is auctioned off, expect more aggressive modulations and higher FEC rates. Certainly won't be sorry to have a larger and more efficient reflector and feed.
It looks like the prices went up since the last time I looked (about a year ago). That's kind of strange considering that not many people are going to want to spend that kind of money on a "non-essential" item with so many people out of work.12 footers are out of stock on that website. I'm looking at one myself to replace the 10 footer.