Pre-Order nbn for $20 off for the first 6 months on unlimited data nbn 50 or nbn 100 plans. No lock-in contract, no setup fee. For example, nbn50 unlimited data & BYO modem/router $59 per month for 6 months.
Offer only valid to targeted premises for pre-order of nbn. Sign up online or call 1300 180 905.
You should get more responses if you ask the question in the Computing or Internet forum.
Asking for best anything is a dangerous exercise. Best in terms of what criteria? Performance, reliability, price, value for money, or something else? Best for ABB is for you to take its supplied model because it will probably arrive pre-configured and tech support will be most familiar with it.
Assuming FTTN/FTTB is the type of nbn you will be connected to, Compliant nbn™ FTTN/FTTB VDSL2 Modem/Routers is a good list to begin your search. For top performance and reliability but ignoring the cost factor, best practice (jargon for recommended/correct procedure) is to operate the modem/router only in bridge mode and team it with enterprise grade router, switch, firewall, and wireless access point. Prices, however, increase extremely quickly. Better yet, forget about that list of consumer modem/routers and add a VDSL line card to an enterprise edge router.
For example, since this user asked for suggestion for "best nbn router" with the sole criterion being faster download speed, so my recommendation starts at ~$7500 on eBay.