In using Model method of solving maths question, we are using visual blocks to scope our thinking. This is followed by analysis through the models.
Models become a link to our thinking process.
The demerit is when we did not create the Model properly, or miss out some details that cause the model to be represented wrongly.
The merit is that it can be simple and straight forward when drawn properly. It reflects outright the relationship between many unknowns.
Less workings is thus needed, as visual que sets in.
For algebraic variable technique, the unknowns are pre-defined and booked as "letters". A space, mentally, has been reserved for the answer.
The working is just simply to accept that the answer is already there but only not numerical. Following through the working steps will ultimately reveal the letter of its numerical data which is what we want.
Variable as letter is good in the sense that we need less analysis, but just mechanically following the rules and steps leading to the final step, of course with some logic and mathematical strategy.
Each has its own advantages and weakness. It is up to us to make use of them in the correct way.
Experience is the only way to overcome the proper selection of which technique.
Thus practice to gain experience in maths is one good way to master maths.
Skiving is a no-no.
Through practice, you will sooner or later find that maths is interesting.