In the picture below there are two keys, actually three if you count the Begali Adventure key on the KX3. Also in the picture, on the left side, is the Te Ne Ke and next to it is the Micro Key. Clearly a size difference, but also a weight difference. Also in the picture is the KX3 (160 - 6m)and the KD1JV designed Mountain Top'er Rig (MTR), (40m/20m CW only). Again, the bigger radio brings more options, the smaller one easier to carry.
Below is a picture of the two versions of the LNR Precision 40/20/10 EFHW. The larger one to the left is the MKII model and the one on the right is the "Trail Friendly" model which uses the 40m coil as a wire winder (brilliant). I've used both and the perform identically as far as I can tell.
Of course you must have an antenna support. Below are three telescoping poles to choose from, a 33ft. MFJ Telecsoping Pole, a 20ft Black Widow and a 13ft Spirit of Air. Again, size, weight and optionality.
So many options and so little time. As WA0ITP says, "I like this radio stuff".