pot scrubbies have way more surface area...but lava rock can work.
Anything solid and non toxic can be used as biomedia...you just need to adjust the amount used until you acheive desired results....based almost entirely on two things; your stock level and surface area of the material is being used as the biomedia.
To that end,and mostly to save space, it is a common practice amongst aqauarists to get the biomedia with the highest possible surface area that is affordable for them....usually pot scrubbies.
I would personaly only use lava rock if i were getting it for free and putting it on a lightly stocked tank....or if it were the only thing i could get...otherwise if you are actually buying the lava rock then I would use something with more surface area and similar cost.
In short: it will work as shown above but there are much better options....