What is best machines?

Proper robot articulation (head, balljointed/unversal jointed shoulders, elbows, hips, and knees) came with G2, specifically the cyberjets, laser rods, and hero leader figures. Balljoints and universal joints had been used way back in G1 (I believe it was Astrotrain who was the first Transformer with ball joints) but never in conjunction across all the major joints. Beast Wars made this the norm across the entire line (the only exception I can think of is that power hugging thing, the one that had its shell halves as its arms).

The initial wave of Beast Wars toys definitely did prioritise beast mode looks over articulation although generally you could get some articulation out of the animals as usually at least one pair of legs was also the robot legs.

To be honest about the time we started getting almost fully articulated beast modes was when the first Transmetals and Fuzors came out (compare basic Terrasaur with the Transmetal version). By the time Transmetals 2 came out there was a very good level of beast mode articulation. Some of the Beast Machines toys had more animal mode ariculation than their Beast Wars counterparts but then that varied from toy to toy and was often because all 4 animal mode limbs became robot mode limbs.

Articulation line wide stayed as the norm for RiD (surely the most underrated transformers line ever?), but went out the window for the gimmick centred Armada. It made a comeback in Energon and has generally stayed since then.