I made some pictures that show similar miniatures from different editions for comparison.

The following picture is a comparison between Knights Errant and their former equivalents.

On the left is a Feudal Knight from 1987 (2nd edition) from the "F7 Feudal Cavalry" series. The whole model including the horse is made from metal. The model is in 25 mm scale and even for that the horse looks very small.

The second from the left is a Chevalier Rampant from 1989 (3rd edition). He is similar to a Knight Errant as the Chevaliers Rampants were described in the army list as "young knights". The horse has no barding and is bigger than the later horses with barding. The horse is very wide at the saddle and the knight looks somewhat like he is sitting on a "barrel". The horse model was also used for the Empire and for Chaos Knights.

In the middle is a Bretonnian Knight from 1990 (also 3rd edition). It is not specified which kind of knight from the army list he should be so I assume he could be used for any kind. The horse model was also used for other races (High Elves for example).

The second from the right is a Knight Errant Champion from 1996 (5th edition) and should be well known. This is the last model that was made from metal (the horse is made from plastic of course). This is the first time that Bretonnians had their own horse models.

The knight on the right is a Knight Errant Champion from 2004 (6th edition). He was built from the Bretonnian Knights sprue and is completely made from plastic. The horse is bigger than before and has about the same size like the unbarded horse on the left.

The following picture is a comparison between Knights of the Realm and their former equivalents.

On the left is a Feudal Knight from 1987 (2nd edition) from the "F7 Feudal Cavalry" series. The whole model including the horse is made from metal. The model is in 25 mm scale and even for that the horse looks very small.

The second from the left is a Knight from the King's Retinue Box from 1989 (3rd edition). The horse has no barding and is bigger than the later horses with barding. The horse is very wide at the saddle and the knight looks somewhat like he is sitting on a "barrel". The horse model was also used for the Empire and for Chaos Knights.

In the middle is a Bretonnian Knight from 1991 (also 3rd edition). It is not specified which kind of knight from the army list he should be so I assume he could be used for any kind. The horse model was also used for other races (High Elves for example).

The second from the right is a Knight of the Realm from 1997 (5th edition), a less known metal model. The Knights of the Realm plastic models were more common by far, because they were included in the Warhammer 5th edition boxed set. This is the first time that Bretonnians had their own horse models.

The knight on the right is a Knight of the Realm from 2004 (6th edition). He was built from the Bretonnian Knights sprue and is completely made from plastic. The horse is bigger than before and has about the same size like the unbarded horse on the left.

The following picture is a comparison between bowmen/archers.

On the left is an archer from the "F4 Feudals" series from 1987 (2nd edition). In the "Red Catalogue" he is listed as a Bretonnian model. He is in 25 mm scale.

The second from the left is an archer from 1990 (3rd edition). He is already in 28 mm scale.

The third bowman from the left is from 1996 (5th edition) and was included in the Warhammer 5th edition boxed set. It is a question of a very common plastic model.

The second bowman from the right is from 1997 (5th edition), a less known metal model.

The bowman on the right is from 2004 (6th edition). He was built from the Bowmen sprue and is completely made from plastic.

The following picture is a comparison between halberdiers.

On the left is a Brigand from 1990 or 1991 (3rd edition). It's the only 3rd edition model with a halberd.

The one in the middle is from 1997 (5th edition) and is made from metal.

The model on the right is from 2004 (6th edition). He was built from the Men-At-Arms sprue and is completely made from plastic.

The following picture is a comparison between spearmen. All models are made from metal.

On the left is a spearman from the "F4 Feudals" series from 1987 (2nd edition). In the "Red Catalogue" he is listed as a Bretonnian model. He is in 25 mm scale, but doesn't seem to be smaller than the others. 

The one in the middle is from 1990 (3rd edition). He is already in 28 mm scale. 

The model on the right is from 1997 (5th edition). In 6th edition there were no new spearmen models released, though the option is still in the army book.

The following picture is a comparison between foot knights. The first 4 models are made from metal.

On the left is a knight from the "F2 Lords of Battle" series from 1986 (2nd edition). In the "Red Catalogue" he is incomprehensibly listed as an Imperial model, but the helmet crest obviously speaks for itself. He is in 25 mm scale.

The second from the left is a knight from the "C26 Feudal Men-At-Arms" series from 1986 (2nd edition). In the "Red Catalogue" he is listed as a Bretonnian model. He is in 25 mm scale.

The knight in the middle is from 1990 (3rd edition). He is already in 28 mm scale. 

The second knight from the right is from 1998 (5th edition) and was originally released for the board game "Warhammer Quest", but was later also released in a blister for WHFB.

The model on the right was built by myself from parts of different 6th edition miniatures. He is made mostly from plastic, but the sword arm and the shield are metal. In 6th edition were no new foot knight models released, but the 5th edition models are still available.