i've never seen a 25 man make any money. however 38 mans i see hit top of the charts... i've looked through every single rig many times counting to see how many employees they got as i was curious before buying one of what rigs can make.
38 man without (assuming you know what reasonable wages are and aren't doing what 99% of rig company directors do and pay employees more money than you actually make) but make purchasing CNC your absolute top priority.
In all honesty, it may be more beneficial to use the money you'd have to spend on a 38 man rig to save up a little longer and get both at the same time. TCSB and GRN are both in exceedingly good investment positions right now especially if you have that amount of capital and don't mind the extra wait.
38 would help you rank faster, but ya maybe like bogie said use the money to make more while you wait, i wouldn't put all your money into the rig. i made that mistake i have nearly all my cash invested into a 50 man rig so it's hard to make money doing other things that are more reliable sources of income like trading as rigs seem to be random sometimes with the payouts.