always go for x4/x5 if you can, otherwise pick the match that suits your situation best! e.g.
1) if there are 1 or more attack/sp attack tiles around, prep yourself with a def and/or counterattack tile
2) if there's only 1 attack/sp tile, you can either just use the tile so your opponent won't have any, or also do def/counterattack
3) watch your health and energy :)