The most important difference is that Viasat uses a couple of GEO satellites where Starlink uses a massive swarm of LEO satellites.
Viasat's satellites are flying just short of 35,800 kilometers over the equator, which means that your absolute best case scenario user standing right next to a gateway, both directly under the satellite, bare minimum latency connecting to an internet server is almost a full 500 milliseconds. Users not close to the equator can add a fair bit more.
Starlink's satellites are flying around 550 kilometers over basically everywhere with 53 degrees of the equator, so anyone who has a gateway close enough to not need to use the inter-satellite link can get 20-40 millisecond latency to the internet in real world usage.
They only recently enabled end user access to inter-satellite links so I haven't seen any real world tests on that but it could be a lot worse than single-hop while still beating GEO.