1.There are 2 u's:
A. with a vertical line on the right

B. without a vertical line on the right

2.And there are 2 a's:
A. Consolas' type

B. Monaco's type

As programmers will be easier (to use less time) to recognize if the fonts are fit to their usual handwriting habits learned from childhood, maybe u with a vertical line on the right (which is also benefit for Greek letter 'μ''s display, see #244 and #336) and the Monaco's type for a (which is also more simple) are better?