Usually the lighter rod will be longer. They may have used the same blank but for the heavier one they lopped a couple of inches off the top
Its not a good way to do it as you end up with one has a really nice action and the other is a "tippy" or the shorter one will be stiff, but that may not be a problem for distance casting
What it may feel like one will feel really nice but the other will not bend properly under load.
You can sort of fiddle a little with blanks by cutting a little off the tip & or the butt but its a bit hit & miss. I assume if they are both by the same manufacturer, they haven't compromised too much
Load them both up to what the manufacturer says and look at the curve and if they have cut the tip the bend will be a bit closer to an arc.