SVG Air is essentially a private charter. (full disclaimer, I have not used them). svgair.com

If you talk to them in advance about your baggage needs they will accommodate you.

LIAT, on the other hand, is an airline that books seats. If the plane gets too heavy they will bounce your bag(s). When your bags show up will be anybody's guess. Hopefully the next flight. It might be later that day, of maybe the next day.

If they don't have enough people on a flight, they will cancel the flight.

You won't know any of this until it's "too late."

Planning close-connections between planes, or between planes and boats is planning to fail.

So yes, there's a big difference between them.

The safest way to go, with LIAT, is to add 1-day buffers in your travel with them.