The liquid-filled balloons may well be less comfortable. There have been " side effects ", like ulcers, severe nausea / vomiting, and spontaneous deflation. The gas-filled balloons do appear to cause relatively mild stomach cramps and nausea.
The various balloon devices available come at a cost, and just like any other attempts at weight loss, need patient motivation. They’re also only intended for a few months’ use, in patients with severe obesity where nothing else has worked. More studies are needed to show how effective they are at long-term weight management.