Which is better? Go for a trifecta or First 4? I am still scratching my head.

How much should I put on tri or first 4?. Have some many combo in my mind.

a) Box 8. 338 units = 168 for 1/2 unit.

b) Have confident of 1 placing selection and box that (stand out) with 10 horses. 90units X 3. = 135 for 1/2 unit.

c) Select 3 confident selection and box with 8 horses. 3/8/8, 8/3/8 and 8/8/3.
126 X 3 = 378. = 189 for half units.

d) 5/10/10. 360 units. =180 for half unit.

e) As what rabbitz has. 300 for half a units.

have manage to cut down to 10 selection af of now. keep going...Pls advise.