Yes, you should always use the angle functions for angles - I think in Construct angles can, at times, go over 360 and below 0 anyway (eg. 405 would be 45 degrees) so straight comparison as numbers will never be reliable. However, the angle functions always work properly with any angle inputs, taking in to account wrapping and angles outside the 0-360 range.
If you want to check if an angle is equal to a number, for example, you'd have to just check the anglediff() expression and see if it is within 1 degree (say) of the desired angle. As mentioned above, both anglediff(46, 45) and anglediff(406, 45) are 1, so it takes in to account wrapping, which you cannot do by ordinary comparisons.