Not using your listed ones, but have a stainless steel conical (from the days when they cost a bit more!).
Secondary fermentation vessel? Na. Just open the bottom valve to purge out all the gunk in the conical section and slap on a air lock. Syphon tubes are things of the past too, just open the "racking" valve and pipe directly into the casks (actually have a little pump to help this along). I can fit one of those stainless steel air stones into the bottom valve (1/2" bsp) and aerate the wort at the start (okay, those ss air stones need a bit of wack, so had to get a 12V car tyre pump, some serious sized filters, and a 20A 12V supply to do this). Does it make better beer? Well the fermenting beer doesn't get mucked about with so much, and I was never entirely happy with plastic buckets, so perhaps? But it's the niggly little jobs I don't have to do any more (and that always got put off to another day) that makes the real difference.
Disadvantages? Mines a 65 litre fermenter: I can do 40 litre batches, but nothing smaller. And they are a bit more fiddly to clean because they're heavy (and careful what you use, I left some steriliser in it the first time it got used; panic and dismay, but got put right). And... they're still flippin' expensive!
Moving it when full also could be a problem unless it was on wheels.:wha:
