To claim pro dancers never make mistakes would be like saying never never forget their lines! Of course they make mistakes, it's just that they will probably be experienced enough to cover them up and carry on (like actors will ad-lib) & few onlookers will be any the wiser.
With the scd pros though, they have to be aware that their celeb partners, who are not experienced dancers, may make mistakes and it will down to the pro to try and "conceal" the celebs errors.
As to which pros are good ..... I think they have different strengths and weaknesses. Some have specialised in ballroom, some in Latin, few in both.
Vincent & Flavia competed in all 10 dances, and were champion Argentine tango dancers.
Ian specialised in Latin, but his family background is dance school, where he was surrounded by as much ballroom as Latin, and also where he saw raw beginners taking their first lessons (and even teaching them) so he had the added advantage of knowing how to teach real beginners.
Matt - also Latin as a pro, but was also a good ballroom dancer as an amateur, so ballroom was not a problem.
Brendan - also great Latin dancer; his ballroom when he first started in the show was very poor, but he has accepted help and improved no end.
Camilla - (yes I know, like Matt, she has left!) danced well with Brendan at Latin, but her ballroom was very weak; but she recognised this and got outside help with both technique and routines.
Darren & Lilia - dancewise, Lilia was the strength in that partnership tbh; but like Ian, Darren comes from a family run dance school background, so used to teaching, seeing beginners.
Natalie - I think is a great all rounder; and is very clever with her choreography. I'd say she is the best female pro the show has had. (Other than Hazel Fletcher, but she left the first week of the first show, so hardly counts!)
Katya - great dancer; her weakness, imo, is that she tries so hard to be different that it doesn't always work - as with the A.Smooth.
Christina - fabulous Latin dancer, weak ballroom dancer - yet to see proof she can teach well!!
Artem - fabulous dancer, and probably the best choreographer the show has ever had; weakness is that he sometimes gets a bit too stage-show dance, as opposed to bb/Latin.
Robin - sometimes I thinks he looks wonderful, other times.... what? He was never a wonderful competitive dancer before he went into Burn the Floor; tbh I think he would look a great deal better if he lost some weight. Muscles and ballroom/Latin - not really a good mix.
James & Ola - Both Latin specialists who have grown into good ballroom dancers. Ola is great at choreography - perhaps helping James and Pamela?
Anton & Erin - they were always 'good' ballroom dancers, never great. They looked great on the show because all the others were Latin specialists. However, where the Latin dancers have upped their game with the ballroom, A&E have not done the same with their Latin - in fact I would say Anton has made no attempt to improve at all. Erin is better, but her technique is weak.
Can't think of anyone else - sorry this is so long, but someone did ask .............