really depends on what type of cleaning your doing,
portable 100-250psi - pump up or battery sprayer is fine
high performance portable 250psi- 1000psi adjustable - inline sprayer
entry level truck mounted - inline sprayer
large tm - inline sprayer
the advantages of an inline sprayer are:
more even spray pattern, less pumping, charging, etc. you can spray a room down in 2 min or less with an inline and spray down solution hotter. which matters on horrific cleaning situations or heavy grease.
inline sprayers are more up front but have their place, we use a hydro force revolution so we can change jugs of concentrate quickly and adjust for the proper dullution, or up the dilution of chem if its really bad.