I think cnd shellac in particular is a big draw, as it's what people know and associate with gel polish, I've never used cal gel, but I know shellac doesn't stay put on my fingers (nor does bluesky or gelish) but so far I have tried gellux and opi, both apply beautifully and stay on my nails, so they are the collections I'm working on building, (opi is another salon name that clients recognise and love).
It comes down to what you want to do with it, CND offer the system with hard gels, but so do gellux and other brands, but do you just want to work with gel polish for now?
Also for me ease of getting hold of products was important, so I chose brands that I could buy (or order) from my local capital hair and beauty, or Sally's (which you should be able to gain access to, to look around with your manicure certificate)
If your north of the country, there is also light elegance- they have a whole quailification scheme, but there potted gel products are amazing!
