Sine Tempore is a space campaign game released in 2019 where your party of four heroes are scouting out a new planet called Primevus V in search of a new homeworld. In 2023 a new game called Nova Aetus was released using very similar mechanisms and set within the Italian Reneissance. Both are miniatures heavy games with tiles, three dimensional terrain and dice rolling.
Sine Tempore has a 10 mission storyline including occasional branching paths, with the missions interspersed with 12 exploration scenarios which have more random set ups each time and with different enemies and scenery. Completing these explorations will help you take control of 24 areas on the planet map and gather important resources which you can use to upgrade your spaceship or equipment.Nova Aetus has a larger mission book with a branching path storylines and optional side quests. Both games are played with 4 heroes every game, so you are best set up with a decent group size, as is not overly solo friendly. 
Component quality for both games are really good, the models are great quality with pretty hard plastic and nice detail, and tiles are a mix of large and small with good artwork on them. The three dimensional scenery is great too with buildings, trees and bushes that stand out alongside the models, and provide cover and objects to climb on. It is a great looking set up on the table.
The core boxes have choices for heroes, with unique roles, skills and upgrade paths with branching choices. Sine Tempore uses boards and tokens while Nova Aetus uses cards, but the latter ulitimately felt more cunbersome in the end and easier to forget your personal missions and objectives. In Sine Tempore enemy models can represent more than one card version which increases the variations available for each mission, and AI is medium complexity for Sine Tempore. There is only one card per enemy in Nova Aetus but has more complex responses, and again in the end Sine Tempore was a preferred experience as often the Nova Aetus has many enemy triggers to remember or keep looking up, Both games use enemy objectives and hero threat dials at their core to drive the enemy actions, and there are a lot of symbols for skills and conditions so this takes some learning and remembering. We found Sine Tempore has a more intuitive approach with Nova leaving more questions to answer. 
Gameplay turns are made on a time wheel tracker, you have action points to spend each turn rather than a set number of actions, and so it feels like you have more choices on how to spend your turn. If you want to take a quick shot and let your turn come around a little quicker then you can opt to do this. Your attack and defense are completed via dice rolls, you score hits by rolling certain symbol combinations, with mitigation largely through gaining extra dice or re-rolls. Tactically speaking there are some considerations, such as standing in defensive cover, focusing dice from an easier attack in Sine Tempore to use later, or in Nova you can gain extra dice to roll. Generally you will not do massive damage combo hits, and you must use attrition or group focus attacks to take out the most threatening enemies.
There are a lot of upgrades choices available, Sine Tempore has space ship areas to visit areas to get new equipment and upgrades, while Nova has a city encounter board and travel events. Some expansions for Sine Tempore such as Kyrone and Motherfang offer a short series of missions to fight a Nemesis boss, with rewards for success and were a nice theme addition, and Nova Aetus also had mini campaign boxes to explore.
Why i chose not not keep them …
SIne Tempore has a ten mission story which was really fun to play as a group, however the side quest mini explorations for resources soon became more of a chore we wanted to skip and I would have preferred a longer storyline with resources simply collected on route or at a mission end. Nova has more of a branching path book so you need to play multiple times to see everything, but did address the resource collection issue from Sine Tempore. In both games you do need to have four heroes, so this can be a limitation but it was not too hard to operate two characters. The momentum turn tracker provides a great feature, the skill upgrade trees offer nice choices and it’s three dimensional scenery, tiles, artwork and general appearance all make the game feel alive and engrossing.
In terms of which game i preferred, Nova Aetus has a slightly deeper storyline, using campaign story cards and more complexity and equipment, however this all comes at the price of longer set up and more rules referencing and we never often felt the need to remind outselves how we rolled for attack or defense. Nova Aetus is a fuller game and a little more refined especially in terms of resource or loot collection, but overall i enjoyed the ease of play and setting from Sine Tempore more as it was was more fluid, with the exception of resources missions which we just ignored in the end. I have enjoyed my time with both games, and they are very similar in mechanics, but my personal vote goes to Sine Tempore for its easier play style. I enjoyed both games, but there feels little need to replay the campaigns once done versus playing a new game.