I have the Apex bars but have not used the Convertibars. According to their site the Convertibars look like they will be fast to adjust but I can't see that the Apex bars will be any slower. I wonder how many folks actually change height once installed.
I have the 3" riser set and know that they raise the bar height 1" above the stock SV clip on height. Therefore, I would guess the 4" bars will get you 2" up. For the 3" set you will need stock + 2" longer throttle cables but the stock clutch cable will just work. If you use the 4" riser you will need stock + 3" throttle cables and at least stock + 1" longer clutch cable. It sort of depends on where you end up placing the bars fore/aft but these cable dimensions are very close to what you will need.
The Apex set is very good in terms of quality, adjustability and parts are available and easily replaced. I would seriously consider them.