Yeap, the Dweller sure looks smaller, size is different. However, the steelfish does not sit on the wrist comfortably for me (I've got a 7 inch wrist) and I find the case design awkard. In case you're wondering, I've considered the Steelfish before as well before I bought my subdate and then my dweller. IMHO, subdate sits more comfortably... for dweller, it will be pretty uncomfortable at first because of the thicker case and the weight distribution, but after you 'break-in' the bracelet (I think it'll take a year), it'll fit nicely....
For myself, I might be biased and as much as this is a Rolex thread, I've got my other likes... Panerai, IWC and Richard Mille.
Maybe u'd like to look at it this way... Brand new Superocean steelfish will set u back by about 3k+. Top up a coupla hundreds and u get a pre-owned Rolex Submariner (non-date though), maybe a 'Y' series.... If u realise u still like the Steelfish after u get the sub, u lose only a wee little bit on the submariner if u need to sell it to acquire the steelfish. But if u're thinking the other way around, it's definitely more difficult, cos the resale value of a steelfish is close to crap.