NB Rebel V5 or Saucony endorphin azura for interval and tempo runs.

NB Rebel V5 or Saucony endorphin azura for interval and tempo runs to add to rotation. Using Nimbus 27 for long runs and Magmax nitro 1 for Easy runs. For 6.00 - 7.00 min per km range workouts not too fast as just started running about 6 months back. Note - Tried NB5s but felt they were too soft and bit unstable. Any suggestions/advice from runners who have experience with these 2 shoes would be helpful in deciding. Thanks.