I'll agree. Stainless steel lines are a major improvement as they don't expand as much as the stock rubber lines, which transfers more hydraulic pressure to the caliper. That said, even with stock brake lines, I usually avoided the rear brake because it was too easy to lock up with just moderate braking. I still, even after swapping all the lines for stainless, lead with the rear and end with all front usually. Once I grab the front brake lever about half the way to full pressure, I'm already off the rear brake. Or if I just need to make a gentle speed correction ("Oops, doing 55 in a 45 and that kind looks like a cop 6 blocks ahead") that I don't want the telltale nod of the front brake, I'll ease on the rear. From the outset, rear brakes generally account for 30% of braking to start and diminish from there as you brake harder with the front until the rear lifts off the ground (not noticeably to the outside observer, but just enough that rubber isn't contacting pavement). Picture the physics in your head: as you brake with either wheel the bike pitches forward and if only braking with one wheel, the braking wheel is the fulcrum. Just the rear, the bike pitches forward and loads the suspension on the front wheel. Again, the bike pitches forward and the pivot is the rear wheel. So, the rear wheel loads the front, but the front unloads the rear. Again, the bike pitches forward but now the front is the pivot point. This is why you have one rotor, caliper, and set of pads on the rear; and two rotors, calipers, and sets of pads on the front.
I say all this to get to this: I replaced all my stock rubber lines with stainless when it was time to replace the lines (every four years for rubber) and I have a hard time not locking up the rear. It's become close to useless except for light braking as I mentioned above. Even with stock lines, if the light turned yellow right at the edge of my safe point to blow the yellow, I'd lock the rear if I stayed on it past grabbing the front. With stainless steel braid, the fronts are night-and-day though. So, upgrade the fronts to stainless, flush fluid (you'll have to anyway since replacing lines), and you'll notice a major improvement in braking. Replace the rears only if you like the lines to all look the same but know the rear will be touchier and more prone to locking up than stock.
I went with Galfer SS lines. Know they offer two types for our bike so you can plan it out. One is stock: one line from the master cylinder to the left caliper, then one from the left caliper to the right caliper; the other is two lines from the master cylinder to each caliper. I opted for the stock since the hose clamps on the bike are set for securing the lines that way. Also, if you email them they will send you the bushings you need for holding them securely in the clamps.
