Blitz. It may be slightly slower, but the normal butler is cheaper if you take into consideration 5K for 8 TRIPS.
Also:
If you make Varrock teletabs, you need either an air or fire staff, law runes and money to pay the butler.
Crude inventory diagram 0001
--------------------------------------
R = Runes
G = Gold Coins
X = Soft Clay
R R G X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
By my reckoning, that leaves 25 slots. If the Demon Butler can carry 26, you are wasting money (38.46gp per inventory). If there is such thing as the 'Steam Staff' like there's mud and lava, then that'd work, but there isn't.
Overall, my brown townysis of your guide reveals that it is better profit to mine 280 iron ore which is cheaper (0gp if you use bronze pick), quicker (even with bronze pick) and house tab making is boring and repetitive (mining is too, but it involves some moving around).
And so, to get the most profit, and fit into your inventory, you need the following.
(Using Normal Butler)
Per Tab:
Inventory
------------
1 law rune

1 soft clay
31.25gp
Wielding
-----------
Air staff

What does it make? You guessed it!
CAMELOT TELEPORTS! 