Also, a more riding-based perspective--since you're new to cycling as sport, Tiagra up is a valid decision. The new Tiagra group is highly functional and reliable; many roadies' issue with it is that it is "only" 9-speed. Note, however, that 9-speed chains are cheaper than 10-speeds.

Late model and brand new 105 is entry-level race quality group, except it is built to take a daily beating for many thousands of miles, unlike top-end race equipment (DA is said to be finnicky without constant management, as it is high-precision equipment; I cannot assess this personally).

If you can get 105 (or better or non-Shimano equivalent) at a good price point, absolutely do so, because it will make upgrades easier in the future. If you are realistic about your riding intentions and current skill-level, though, you'll probably have a TON of great miles on Tiagra equipment.

And, all that said, even new Sora isn't bad, depending on what you're coming from. If you're brand new to road riding (for sport), Sora will feel like the PB&J of cycling components...but you'll quickly learn that it has a variety of functional/ergonomic/value deficiencies.

Don't buy into hype. Ride what feels great, and just be aware of the hierarchy.