Isomalt and sucralose are both artificial sweeteners, ie. Created chemically.
On paper, and on some peoples meters, they may not raise blood sugar but I, for one, am being very sceptical about what long effects they may prove to have on our bodies and our health.
They haven't been around in the human diet very long in evolutionary terms and I suspect we may just be building up problems for the future.
Other sweeteners are similar.
Proponents of the real food and anti food addiction movements would also argue they keep our taste for sweet things high, making it more difficult to resist anything else sweet as well
So all in all, I try (and sometime fail) to avoid them. They might be a useful crutch initially but there are so many people out there now using sweeteners as an everyday alternative to sugar that I think we might just be replacing one problem with another.
Just my very personal opinion, and posting as someone guilty of falling of the wagon herself yesterday