I can't speak to the difference in comfort, but the queen + king size slats come in 2 pieces - a left and right side.
If you use the slatted bed base LAXEBY, it's got a "frame" around the perimeter, which might or might not fit in your current frame - you'll want to measure carefully. The sections of the 'frame' would need to be correctly supported by the edge and along the center.
The LIARED slats are connected together
/a sort of rubber strip along the edges. Again, you'd need to measure carefully to make sure they fit correctly in your current frame.
You might need to bolt a strip of metal or wood onto the frame if the IKEA slats are not wide enough.