Looking at the images the Optus speedtest has been done while connected as 3G. The Vodaphone test is unclear (looks like a linked chain?). Something different anyway - perhaps set your Optus unit to only connect via 4G and rerun the tests. Are these mobile phone or mobile broadband readings?
Yes Optus meant to give you 4G but this is what you get. I got a connection with Optus and this is what I got and same time speed check with a VODAFONE the speeds are incredible.
This morning with Optus, it’s managed to get to 5-6 MBs but VODAFONE 116MBs. No explanations will justify optus’ internet speeds. It’s just crap.
Optus don't make any representations on mobile speeds. That said, your experience suggests either you are in a fairly remote location or there is an issue with an Optus tower or your phone.
I live in Curtin, ACT. At my work place, I can only watch the spinning wheel, while my co-workers whom with Telstra and Vodafone surf the web and watch youtube videos. I don’t live in dunny doo or woop woop mate.
If the Optus supplied service is limited to 3G, it's very likely that one of @petergdownload's answers is the likely cause.
Could it be that there's no Optus supplied 4G service available where you are, or that your handset doesn't offer support for Optus LTE?
I'd run a coverage check. Enter the IMEI or model of your handset. We'll let you know you of the sort of coverage you can expect to receive in your area.
Optus 4G bands:
If you have any other questions, send them through. We're happy to help.
I live in Curtin, Act and got an iPhone XS Max. This is not something new. Probably last 6 years or so I have been raising this issue of limited coverage or no coverage but the at the same time, I see VODAFONE and TELSTRA has faster coverage. I switched to VODAFONE two years ago and didn’t have coverage issue. So it’s with your service issue not my phone or where I live. This is true of my home internet service too , my home internet bundled with Fetch Tv constantly coming up error message.. ‘No internet connection or slow internet connection ‘ This is the explanation I got for last few years and no improvement to internet service mean time. No Usain Bolt speeds here!