I have the Lowndes and wear them often, but they feel too casual to wear with suits in my opinion (mine are brown).
I wear them exclusively with odd trousers - grey flannels, linen, etc.
I would get the cap-toe oxfords first as you'll get much more use out of them and the Lowndes later, if you find you'll be wearing odd trousers outside of work hours.
I think even brown oxfords will be worn less by you than black ones - it seems you're currently more comfortable with black.
However, I believe you'll get to the point where you're wearing the brown ones more often.