If the big wattage inverter is at a low price or even free, grab it. The number of batteries and how fat the wiring and fuse size has to be depends on what you are actually running with the inverter; not on what the inverter "could do."
Also, I find with my 3000w MSW inverter that it has no more additional draw on the batts running low watt appliances than a lower watt inverter does. There isn't much if anything to be saved there by getting a smaller inverter to run smaller things.
AFAIK from much time on this forum, the high stand-by draws of high wattage inverters are actually being quoted for inverter/chargers, with their huge batch of electronics to run their remotes and a zillion settable features. You see 2.3 amps or whatever. My 3000w inverter has a no -load standby amps draw of 0.5 amps.
It also has a remote on/off switch, that I use so when I am not inverting anything, I turn it off. Why leave it in standby? (Watch the TV set though. If you invert to run your laptop, the TV will be on in standby eating extra amps. Unplug the TV.
In actual use, the 3000w inverter draws fewer DC amps to run a CFL reading lamp than a 150w inverter does. Turns out that is because the 150w inverter is plugged into the Winegard 12v socket with long thin wires to the batteries, while the 3000w inverter is close to the batteries on fat wires.
In other words, "It depends!"