Big boxes w/ chicken knobs look solid. I don't know why but to me, while being more real-estate economical, the smaller ones seem to look like their wide base knobs are too close together and could possibly come undone by an errant foot. I don't really think they are flimsy of course - just purely going by aesthetic impressions.
I've always associated Cornish pedals with the "regular" look, which gets my vote. Not really like the black box design, nor the Fender-type knobs. That said, size is a factor to consider and being that most folks use power supplies, a battery-free smaller grey box would be ideal!
I prefer the small because they are smaller (duh) and have top mounted jacks for my pedalboard, but I do think the bigger ones have the classic look. But still, I prefer the old because pedalboard utility is more important for me than overall looks.