Advantages:

• Exterior: can be combined with other upgrades (siding, stucco, etc), more complete layer of continuous insulation is possible, space is not a limitation
• Interior: easy and safe access to surfaces

Disadvantages:

• Exterior: requires exterior finishing, windows and doors need new flashing
• Interior: requires interior finishing, thermal bridges remain at wall intersections, possible dewpoint issues (1/3-2/3 rule), loss of interior space