Hevy in short
The most generous free tier of the big loggers, a social feed and a Strong CSV import. The downside: pro is needed for unlimited routines and full stats history, and offline use was not verified.
Liftosaur in short
Fully scriptable progressions, with free Hevy CSV import and CSV and JSON export. The downside: apple Watch, graphs and the plate calculator need Premium, and there is no Strong import.
Free tier and price
Hevy free tier: 4 routines, 7 custom exercises and 3 months of stats history. Paid: pro: $23.99/yr or $74.99 lifetime (monthly $2.99 or $3.99 listed).
Liftosaur free tier: programs, editor, logging, history, import and export, measurements and sharing. Paid: premium: $4.99/mo, $39.99/yr or $99.99 lifetime (US App Store).
Prices are the US App Store listings as of the check date, and some listings show several entries without labelling the billing period, so confirm in the store before paying.
Switching between Hevy and Liftosaur
Moving your data. Hevy: Imports a Strong CSV; exports CSV. Liftosaur: Imports Hevy CSV; exports CSV and JSON.
Watch support. Hevy: Apple Watch (watchOS 9+) and Wear OS. Liftosaur: Apple Watch (Premium only); Wear OS not found.
Ads. Hevy: None. Liftosaur: Not verified.
If a game is what you are missing
Neither app has a game layer. We make GYM RPG, which logs the same sets, reps and weight and adds XP, a skill tree and a party boss. It is not a drop-in for either app, because we have no import tool and you would start fresh.