From the Guidelines

IVIG is the preferred treatment for AIDP due to its ease of administration and wider availability, although plasma exchange is equally effective.

IVIG (0.4 g/kg body weight daily for 5 days) and plasma exchange (200–250 ml plasma/kg body weight in five sessions) are equally effective treatments for GBS, as shown in studies 1.
IVIG is usually the treatment of choice because it is easier to administer and more widely available than plasma exchange 1.
Plasma exchange followed by IVIG is no more effective than either treatment alone, and there is insufficient evidence to support the use of add-on treatment with intravenous methylprednisolone in IVIg-treated patients 1.
In resource-limited settings, small-volume plasma exchange might be a relatively safe and economical alternative to conventional plasma exchange, but its efficacy needs to be established in further trials 1.

The choice of treatment may depend on the availability of resources, with plasma exchange being less costly than IVIG, but IVIG being more widely available and easier to administer 1.
Corticosteroids have not been shown to be effective in the treatment of GBS, and may even have a negative effect on outcome 1.
Antimicrobial or antiviral treatment may be considered in patients with GBS who have an ongoing infection, but preceding infections have usually resolved before the onset of weakness 1.

From the Research

Plasma exchange and IVIG are both used to treat Acute Inflammatory Demyelinating Polyneuropathy (AIDP), also known as Guillain-Barré syndrome 2, 3.
A study found that IVIG and plasma exchange have similar efficacy in improving primary and secondary outcomes in GBS patients 3.
Another study showed that IVIG is equally efficacious as plasma exchange in improving disability scores in AIDP patients 2.

IVIG has been shown to hasten recovery in AIDP patients, with a trend towards more improvement with high-dose compared to low-dose IVIG 2.
Plasma exchange has been found to be associated with a slightly higher risk of adverse events and post-treatment worsening symptoms compared to IVIG 3.
IVIG is considered more user-friendly with a significantly lower patient discontinuation rate than plasma exchange 3.

A study found that IVIG showed a slight advantage over plasma exchange in reducing the need for mechanical ventilation and hospital stay duration in GBS patients 3.
In children, plasma exchange demonstrated a slight edge in improving secondary outcomes 3.
Treatment with IVIG is significantly more likely to be completed than plasma exchange 2.

The mechanism of action of IVIG is less clear, but possibilities include antiidiotypic antibody effect, complement absorption, and downregulation of immunoglobulin production 4.
Plasma exchange is thought to act by removing pathogenic antibodies 4.

IVIG and plasma exchange are both used to treat various neuromuscular diseases, including myasthenia gravis and chronic inflammatory demyelinating polyneuropathy 5, 4.
The choice of treatment depends on various factors, including the severity of the disease, patient preferences, and availability of resources 6, 3.