One is not more practical than the other
I always thought of TJs as the most practical types. (Especially STJs)
A definition I pulled on "practical"
1. concerned with matters of fact: concerned with actual facts and real life and experience, not theory "the practical applications of this research"
2. useful: appropriate, sensible, and likely to be effective "practical advice"
3. good at solving problems: good at managing matters and dealing with problems and difficulties "He's terribly clever, but not very practical."
4. practicing: involved in the actual work of a profession or activity
"practical physician"
5. suitable for everyday use: plain, functional, and suitable for everyday use
6. virtual: resembling a particular thing in almost every way ( informal )
"The campaign was a practical disaster."
I think we can probably rule out 5 and 6 as not being particularly relevant. Both SJs and SPs in my mind are quite practical - just in different ways. Both are concerned with matters of fact, good at solving problems and sensible. The SP will demonstrate the ultimate flexibility in pursuit of an immediate goal. That is very practical. They may not be as organized in doing things. That is not as practical. The SJ will pull from a storehouse of previous experience of what works, be decisive and they will be organized in getting it done. That's very practical. They may limit themselves to a pre-conceived notion of what they've done before though and may not be open to potential options (the hammer looking for a nail scenario). That's not so practical. I don't think you can say that one is more practical than the other.
Let's take a situation where you need to conduct a negotiation. I'd much rather have a practical SP on my side than an SJ. They will be more flexible on options that benefit both sides.
You could get into the whole T vs F thing and say T is more sensible or practical than F because of the stronger focus on logical thinking. However, my view is that the way people feel is a fact, and given the importance of emotions in driving human behavior, taking them into consideration is often quite important.