I haven’t ever traded USA options, so I don’t really know anything about the benefits of that market vs the Aussie market.
neither have i, but i have done a bit of research into it in the past, and may dabble in it once i'm retired. from what i saw, there are some obvious benefits of the US options market.
the big one is that the spreads are really good, i mean really really good vs Aust options. on underlyings that are very dollar expensive compared to the largest caps we have in Aust, i was seeing spreads like 3.02/3.04. our closest equivalent is probably CSL, where you will typically face spreads like 2.70/3.50. liquidity is probably much better in the US as well.
i know i wrote above that spreads often aren't too much of an issue as you can still get close to the mid even on a large spread, but that doesn't happen all the time, and derivatives over different underlyings often exhibit different characteristics. in particular i have had lots of trouble getting decent fills for CSL options in the past, if CSL had 3.02/3.04 spreads, i'd just hit the offer to get it done immediately and move on.
in the US, 1 contract is typically over 100 units of underlying, as it is here. however, the underlyings tend to be a lot more expensive over there. what's the difference between 100 units of a $1000 stock vs 10000 units of a $10 stock? there isn't much if trading the stocks themselves, but when it comes to options trading, there is a small but noticeable difference.
firstly, IB charges commissions based on how many contracts you trade, so with expensive underlyings you don't need as many contracts for the same exposure, keeping your commissions down.
the second difference is somewhat obscure, but over the years of trading Aust options, i've had this happen to me several times. i'd be trying to get a fill on say 100 NAB contracts, then someone comes along and takes out 2 or 3 of my order, then the market moves and i have to move my bid/offer in a bit for the remaining 97 or 98 contracts. that creates
another order, meaning i have to pay extra brokerage on the 2 or 3 contracts, and it results in multiple parcels, making record keeping more of a hassle. whereas in the US, even 1 contract on a dollar expensive stock is a decent sized chunk of exposure. i imagine that would help prevent this sort of thing from happening. notably - this never happened to me before they changed the lot size from 1000 to 100 back in 2011 (although i was doing smaller trades back then, so that could've had something to do with it as well).