I think grabby is an inaapropriate term to use in describing the difference between .5 (or.7) and a 1 degree. Grabby infers something is wrong with the tune and the skis don't roll on and off edge smoothly. This is not the case with a properly prepared .5 degree base bevel unless something else is wrong. For example, iconsistent base edge bevel, ie wavy, hanging burr,or extreme linear stone grind pattern not adeqautely polished out of the base edge. The other factorthat can cause grabbiness is skiers canting issues.
So in conclusion, if the .5 is true & consistent , burr free and smoothly polished and the skier has no alignemnt issues the ski swill not be grabby. Will they be ultra responsive to tipping moves. Absolutely! but they wil roll on and off edge smoothly.
If edge to edge quickness was all about technique and and not about the combination of tune and technique, everyone would ski on a more forgiving 1 degree (which actually if tuned as I have described above and is a true accurate 1 degree skis extremely well) It is simple geometry though, the farther the edge is from the snow the more the ski must be tipped before the edge is engaged.
If you definitely want to avoid grabby, then you may not want a lower base bevel angle. I say that because a smaller base angle will make the skis more sensitive to small adjustments when they are flat or near flat on the snow. With a flatter base bevel, the skis may respond to a command to turn that you were unaware of making. This is the other side of the responsiveness coin to grabbiness, which is simply solid responsiveness to edging.
If you're concerned about achieving quickness edge to edge, technique matters more than tune. If you fight or resist letting go of the old turn, it saps the energy of your turn. You'll still transition to the new turn despite your resistance, but you'll be slow edge to edge. If you don't resist but instead release the old turn freely, the energy released from that turn will make for a snappy edge change.
Personally, I put a 0.5* base / 4* side bevel on all my skis, including a pre-flowride pair of peak 78. But most skiers prefer a bit more play ("forgiveness") in the steering. Different strokes for different folks. If you do try a more aggressive tune, do so on an uncrowded slope the first time until you gain confidence that your skill level is compatible with the increased responsiveness.