If you use a while loop then code that is not in the loop will execute while the loop condition is true. For instance if one of the analogue channel readings goes above its threshold then no other channels will be read until the reading goes below the threshold. Is that acceptable ?
Using an if (it's not a loop by the way) then you can take actions if one of the analogue channel readings goes above its threshold then move on to test the next one and take action if required. The next time the first condition is checked the same sequence will be executed.
The difference between the two approaches is that the first is 'blocking' code whilst the second is not. Which is more appropriate to your circumstances is up to you to decide.