Brewzilla 65 or 35

G'day I've been experimenting with single batches in the 65L, they work, but at the moment I've only done 3 batches with a full volume mash, Eff% has been down a bit but that has to be expected, due to dead space and the water/grain ratio. I haven't tried doing a single batch in it with a sparge yet, it wont be a very big sparge but it could make a difference. They have all just been roughly 4.8-5% beers.
So you'll get good beer out of a single batch in 65L, you might struggle with the chiller, I haven't tried the chiller I've been doing no chill. The immersion chiller included would only have the bottom bit in the wort in a small batch.
Hard for me to say what is best to get.
For a 5% beer the 35L is perfect, if you want to brew mostly 7-8% a 35L vessel might be a struggle, though far from impossible.
What size batches do you do? 19L batch would be very small for the 65L, I havent tried that small.
Cheers!