NeTEx uses XML technology; large documents require more processing power to handle than some formats with a lower semantic content, especially if extensive validation and integrity checking is done (though noted that the referential integrity checks can be omitted if documents are known to be correct). In mitigation, computer power continues to get cheaper whereas the cost of skilled resource to resolve issues arising from unchecked data errors has not.
XML is verbose, with both start and end tags being required, and NeTEx documents can be large. Various feature help to reduce size notably; the ability to declare default value at a frame and other levels, and the ability to reference data from other frames, and the ability to exchange just elements that have changed. Bandwidth can be saved by sipping documents for transmission.