I have an answer to this from
ukwhitegoods.co.ukPowder is the original detergent format and to this day it has all the technologies available in it, you get the full cadre of cleaning power in a powder so after that it only comes down to how good it is. I know it’s potentially messy and harder to get home but it really is the best.
Tablets are different as most are hard pressed by a stamp, it’s basically just powder though that is highly compressed. The big problem is that some take quite a while to dissolve and therefore you can’t use them in the soap drawer, except Ariel tablets. You will also need a net or bag for any bar Ariel tablets as otherwise, since they don’t dissolve so fast, they can sit on clothes and the bleach makes short work of any coloured items. So tablets are good in some ways, poor in others.
Liquid is the most convenient in many ways to a lot of people as you just pick up a bottle and pour it in. well, that’s the theory at least.
In practice liquid can cause a lot of trouble, especially for service engineers. You see, it’s easily overdosed and this can cause no end of harm to a machine and that goes back to the tip about dosing on the first page, it really is vital to get it right or expect a bill for the engineer as manufacturers generally do not cover for detergent misuse which is the way they view these problems.
If the dosage doesn’t get you then the smell might, liquid detergents do not and cannot at this time contain a bleaching agent (nor is it ever likely to) so the bacteria doesn’t always get killed in the machine. This can congeal and for a rather smelly mass which is not good for your nose or your machine and that’s one of the reasons why I recommend a maintenance wash and why it has to be done with powder or tablets, so that there’s a bleaching agent to remove any bacterial build up in the machine.
So, Bold 2-in-1 is fine because it has a different softener than the others and the powder is recommended over the liquid. I haven't used Bold liquid but I was using Ecover liquid and my machine smelled very, very rank