The short answer

Compare the moisture-control system, not the label. A vapor barrier can reduce ground moisture when the floor is prepared and seams are handled correctly. Encapsulation is a broader scope that may create a more continuous boundary, but it still cannot substitute for correcting plumbing leaks, groundwater, drainage, unsafe access, or contaminated materials.

Put both proposals on the same table

Scope item Floor barrier only Fuller encapsulation question
Ground preparation Is debris and sharp stone removed? Is the whole floor ready for a continuous membrane?
Seams and edges Tape, overlap, and wall termination? Are walls, piers, and penetrations included?
Water entry What happens with seepage or standing water? Is drainage designed before the membrane?
Vents and access Left open or changed? What is the approved ventilation strategy and access-door detail?
Humidity No equipment or an allowance? Is monitoring or dehumidification included and serviced?
Insulation and pests Excluded? Is damaged insulation removed or replaced?

Take photographs after rain if it is safe, note musty areas, and ask each contractor to mark exclusions. A low price can simply be a smaller scope. Do not compare a membrane on the floor with a proposal that includes drainage, wall work, insulation, and equipment without separating those pieces.

Stop conditions

Pause if you see sewage, active flooding, mold-like growth over a broad area, damaged support members, exposed unsafe wiring, or suspect asbestos-containing material. Crawlspaces also create fall, respiratory, and electrical hazards; do not enter just to collect a better photograph.

Limits

This is a scope-comparison guide, not a local code interpretation, structural assessment, or mold-remediation plan. Climate and building practice change the correct assembly.