Choose a useful strength
For survivability, sort the database by HP. For repositioning, sort by speed. For damage scaling, sort by attack multiplier. The cards below show the leaders in each base stat, so you can choose an available partner rather than follow an unsupported universal winner. Blissey leads base HP at 185, but has 101 speed and ×1.11 attack. Regieleki leads movement speed at 162, with 106 HP and ×1.25 attack. Kartana leads attack at ×1.70, with 97 HP and 124 speed. Choose survivability, movement or damage scaling; none wins every criterion.
Check the starting attack
Every partner can learn Normal moves plus moves matching either of its types. The starting move comes from the starter table when present; otherwise the game selects a move for the first applicable type. A large attack multiplier cannot make a buff deal damage.
Make a fair comparison
Compare partners at equal permanent upgrade levels. Upgrades are per Pokémon, so an upgraded starter can be more useful than a newly unlocked high-stat partner. Take one partner into repeated runs and track where you are losing: crowd coverage, boss damage or movement.