For traction on ice and in hard packed snow studs are a definite advantage but they do significantly reduce grip on wet and dry roads particularly concrete roads by reducing overall surface contact and the stud's inability to bite into the concrete. Using the studs or not would be a question of how often you need that ultimate performance in hard snow or ice grip.
As for siping, tire manufacturers design the tire with the optimum number of sipes and grooves to provide the desired level of traction without affecting wear, ride comfort, handling, and noise. Avoid additional siping as it will affect tire performance and void the manufacturers warrantee.
Whichever you go with, most four wheel drive and all wheel drive vehicle manufacturers recommend four identical tires (that includes studs) to maintain similar wheel rotation otherwise the center differential is working overtime to allow for the different wheel speeds between the axles. Also, cars with ABS brakes won't work properly unless all the tires are similar.
I have 3 cars plus my daughter's car, and all except one car our recently Toyota solara 2005 sle v6 are running on studded Nokian tires, or Pirelli P160. The Solara is on Michelin X-Ice 215/60/R16. I wanted to equip the solara with Nokian studded tires, but at this time of the year, they were not available in the size the car requires. I have to agree 100 % with Jerry our CR moderator. I live near Montreal Canada, and we have black ice and all the crap that comes with it. This season, we already, had very bad weather, with the associated road conditions, that comes with it. As far as handling is concerned, if you or your daughter are driving safely, I do not see any problems driving on studded tires, I am doing it for the last 12 years, without ever having any particular handling problems. I generally slow down 10% in tight curves, and I do not exceed 75 miles/hour on asphalt. Driving on concrete, requires more care than on asphalt. I read somewhere, that the swedishs have over 80% of their cars running on studded tires in winter.