I have read that the straw handling is more critical with the 1/4 cc straws. Since the diameter is smaller, they are more sensitive to temperature change. I am guilty of using fingers to remove a straw instead of the plastic tweezers. In doing that you end up making some contact with adjacent straws. Smaller diameter means you have slightly heated up the end of the straw. So, more risk when handling or transferring. Have read that the 1/2 cc tweezers may not grip tight enough to remove a 1/4 cc straw. So need to purchase the 1/4 cc tweezers. Have read that the universal gun may be a problem over time when the plunger rod gets a little bend in it and may not line up with the 1/4 cc straw requiring you to seat the straw on the plunger rod and then use the straw to push the rod down into the gun. Or purchase a 1/4 cc only gun. Must use a sheath with an insert to ensure a good seal. I have not used one yet, just what I have read. Sort of like the change to metric tools decades ago. You end up with two sets of tools and need to switch between them until all the old semen is used up. Maybe 20 to 50 years to make the full transition.
The smaller straws are supposed to have a slight increase (1%) on per cent cows settled due to the more uniform temperature curve when the straws are frozen resulting in fewer damaged sperm. But, probably offset by the need for better straw handling. Probably will just take some time to get comfortable with the new stuff.