I used to use the slotted ruler a lot, but I have been away from quilting for a few years and forgot that I had it.
I was doing a lot of jelly roll patterns back then, so it was useful.
As for the log cabin trimmer, I don't know. It might be very useful if you use the method of chain sewing your blocks to the new strip and then cutting the strip even with the blocks.
I've found that I prefer cutting the strips to the exact lengths that I need, so that my blocks will stay pretty square - I know right away if my seam allowance or cutting is a little off, because the next strip should fit perfectly onto its place on the block.
After I squared up the blocks for the last log cabin with an ordinary square ruler, I had only a handful of slivers and "dust" trimmed from 100 blocks, and that was much better than I had had with the other method.
Some of these rulers are so specialized and very specific that you almost need to make a LOT of those kinds of quilts in order to justify the cost. I bought the Creative Grids Pineapple trim tool after watching a couple of videos - one of them mentioned 1¼" strips, which is exactly what I want to use.
After I ordered it, I learned that you actually have to use 1¾" strips and that's too big for what I want to do. I'm going to go back to the reverse foundation papers for my plan, but I have another $30 ruler that I'll never use.
The only rulers I really use a lot: 6x24", 6x12", 3x12", 4x48", Square-up rulers in several sizes from 2½" to 22", Triangle Square-up rulers for HSTs, and QIAD flying geese rulers.
Hope you find the right tools for the way that you work.