Insulating the floor is a very good option if available.

By insulating the floor of your attic you cut off that attic space and no longer heat that area.

This also allows adequet ventillation for your roof which will last longer because of it.

Insulating Rafters with prop-r-vents is good to create more conditioned space without loosing the roof ventillation.

The only down side to Prop-R-vents is that the actual vents take up an inch of space which reduces the potential R-value of that space.

You also end up heating more space which leads to higher feul bills.

When you make a "Hot Roof" you are actually stopping the ventilation that flows underneath the roof deck. 

The problems with hot roofs are that they dramatically decrease the life of the shingles.  The insulation behind the shingles trap the heat within the shingles, thus the sun bakes the shingles at a much faster rate. 

 But I use my attic for storage?

You can either...

Blow underneath the flooring and dense pack the insulation into the rafter space

Build up the flooring with 2X6 to allow for extra space.  Run boards perpendicular with existing joists.

Gaps and cracks should be sealed before installing insulation, especially batt insulation.

Bath fan was vented into the blocked soffit, causing the moist air to stay in the attic which led to mold.   

Heat will penetrate the low points in insulation.  Get the most of your insulation by having someone install it correctly