Are you doing a separate AC and Furnace or heatpump?
As far as brand the there's actually only really like 3 manufactures with a ton of brands. Lennox, Trane, and Carrier (I think). Anyhow, like a lot of things, a couple big corporations that buy other brands and then have different level "quality".
From people I know who actually installed HVAC units, going with a mid to high tier is better but the critical detail is installation, especially vacuum and filling.
I ended up going with a rebranded Armstrong heatpump (it's the lower version of Lennox, I have a looooong story about that and this dealer). It's a top of the line 19 SEER unit with variable compressor and fan. It was a much larger cost but so far saving about $50/month but the real benefit is it's far quieter, runs at capacity needed not just on or off like single stage units so much more consistent temps in the house, and of course more efficient. I paid around $15.5k I think for that and then also added accessories. Of course I would imagine a smaller sized one should be cheaper. A regular single stage cheap one would have been around $8k.