Having put my cards on the table, I will share that I have DOT-5 in all my British cars and none have had any seal related problems. I have used DOT-5 in our GT6 for 20 years now without any hint of leaks or seal failure. In each case the brake system had all new rubber installed and the metal lines were flushed. Using DOT-5 is a choice that you should make based on your expectations for the car and weighing all the information that is out there. Certainly one factor to weigh into this is the warranty on new components. Regardless, only implement DOT-5 when starting with clean, new components. You are inviting problems if you don't.
Some of you may know that I had a long association with Sierra Specialties (over 15 years). I found Joe to really know his stuff when it came to hydraulics and the quality of his work was considered to be the best. Certainly his customer service was unsurpassed. With regard to silicone, his advice against it was largely based on the lubrication issue, but there were others. When it comes to replacement/reproduction MC's many have warnings to not use silicone and will void their warranty if you do. In my personal experience, I have seen many mushy seals as a result of use with silicone, and I think that is mostly an issue with natural rubber products more than anything, but you should definitely replace rubber that has been used with glycol based hydraulic fluid. The system should be flushed with alcohol and lots of compressed air.
Other issues I've personally encountered is that because silicone is hydrophobic, any water that accumulates in the system will separate out and collect/ pool in the low spots of a cylinder or reservoir. As a result, corrosion can actually be worse with silicone unless you change it with regularity.
I've attached some pix of a Mini style master cylinder that rusted out, letting fluid escape the system. You can see where rust has enveloped from inside the reservoir, along the seam, which eventually rusted through to the outside. It was just a matter of time until this failure would grow more substantial. With a horizontal bore, this would develop along the floor of the bore. In this case, with the reservoir failing, the only way to correct it was to replace the master cylinder as well as the wheel cylinders.