Both are 4-2-3-1 variations. I like the 2nd one more. Both of them count on ball possession. If you wanna go 4-2-3-1 (eihter a or b) you need very good full backs with red arrows. You must have red arrows on them (DR,DL) because they have a lot of space to run and make crosses. If you take the 1st, if you have playmaker AMC it could be really great. It's a classic trequartista position. Maybe red arrow AMC as well. It's not really that defensive but an all round tactic. You can go attacking as well. If you go defensive of course you have to counterattack. If you go attacking consider the off side trap. You can either focus down both flags or mixed.

If your opponent defends with 3 DC or uses short tactics then go for either a or b. If he has 4 at defense he can counter you in some cases especially if he has good wingers.
A serious backdrop of both these formations is that they can be hurt by wide players that attack wide areas. Therefore, it can be countered by eg a 4-1-4-1 or 4-4-2 variations.