Id say its personal preference. When i did my training we used loose lashes and ive always stuck with them.
During training, our trainer gave us a wee tip - to practice picking up the lashes, get a piece of micro tape, make it double sided and stick it to your pad then put some loose lashes out and stick them in a line on the tape. I used to spend ages doing it and at first it helped when doing lashes cos i had all the lengths sitting ready just to be picked up and put on. Its similar to strips of lashes i guess minus being close together and the stickiness of the strip they are stuck to. Hope ive explained that well enough! Just had a mental block trying to think how to word it
Ive tried using the strips of lashes but find it hard and time consuming, i find i bend them trying to pick them up cos they are so close together - again just personal preference and probably because im so used to loose ones.