The SV stuff is good and remember its getting the customer through the door NDE that counts, if that means useing a decoder then so be it.
They are not all 100% as many think but they are very close.
The union is an easy pick as is the profit, once you get good with the CB pick you will find the invincible easy as well so the slide rule decoder may not be worth getting straight away.
A 114 P+C may be worth investing in as they are the cheaper tool for a common lock but its down to you.
Practice with your CB pick and if you find any locks that you continuely get stuck on then look in to the decoders for those.
The plastercine decoders take some practice and skill to measure and decide the levers and on a lot of locks you will find that certain levers read the same so a bit of messing with a make up key is required in making the various alternitives, you would be better using that practice time on your CVB pick and just pick the lock anyway.