Yes HD414 is the best of both worlds.
It's the center / medium / do-everything pad (it will sound acceptably good on at least every Grados, and great on some of them).
bass / congestion of the sound <--> Flats -- HD414 -- Bowls <--> treble / harshness
Bowls can be "fixed" (become more bassy, and not harsh, which means more comfortable sounding, like the flats) to a certain extent with tape, I've had crazy good results on my SR325i, with 3M Scotch tape (and not the "magical one"), but you need to make sure to cover very much 100% of the surface (the one that is spongy) around the circumference of the pads, or else bass will leak and you'll loose the desirable effect. Using the same pads the effect works best on Metal/Plastic Hybrids > All Plastic > All Wood > All Metal, Grado models. I've tested with SR325i > SR200 > RS1 > HP2. Past the SR200 the effect was barely noticeable on my RS1.
Flats cannot be fixed with tape. Taped flats gives a little bit more bass, but I found it became exaggerate and too much, lol it was almost headache inducing for me, flats are already very bassy without tape. Taped HD414 changes absolutely nothing on their without-tape sound. But definitely I
love taped bowls on my SR200 and SR325i, it's magical how it improves sound comfort, details, and balance... it simply makes your headphone give you more.
Comfort-wise it's: Quarter-modded HD414, reversed > Bowls with PX 100 pads under them > HD414 > Comfies > Flats > Bowls.
HD414, comfies, PX 100 pads I always recommend to have a hole in them for better "liberated" high frequency sounds. Same principle, it makes your headphone give you more. I don't mod my Grados, but I quarter hole my pads (and use them non-reversed).
I personally like the HD414 pads for all my Grados but it's always best to fine tune to your taste. I have a RS1 that has too much bass for my taste, so I use bowls for it. I very much always couple bowls with a PX 100 pads great comfort:
http://www.bhphotovideo.com/c/product/638099-REG/Sennheiser_089331_089331_Earpads_for_PX.html
My old RS1 was the contrary, it had too much highs, I used flats for it all the time, but it also sounded very good with HD414. You really need to experiment.