Not an opinion.
Maths/mechanics:
-You start with a 5 CPS (coin per second) gold mine. Every minute you'll make 300 gold from this mine -- every 15 seconds that's 75 gold.
-Each full wave of zombies costs 120 coins (10 per zombie).
-Each TNT tower costs 100 coins to place and an additional 100->150->200 to go from level 1->2->3->4 (total of 550 coins). Building a mage tower costs 200 coins but the upgrade costs are the same as the TNT tower's.
-For simplicity, we'll assume that the opponent sends 12 zombies every 15 seconds and that each zombie is 15 coins per kill (so 180 coins per wave). We'll assume that they're both well-placed such that the builder gets all the mob coins before the next wave. We'll also assume that the players send mobs every 15 seconds and get their XP before the next wave.
-A mage tower affects
all zombies within the tower's radius while a TNT tower will shoot a TNT at a zombie -- anything within a small radius of the explosion takes damage.
Scenario:
Let's say we have players A and B.
-Player A decides to build a TNT tower and upgrade that to level 4. After the first 15 seconds, he'll have 25 coins (500 + 75 from the past 15 seconds but spent 550 on the tower). He'll send 2 zombies for his wave (now at 5 coins).
-Player B decides to build a mage tower and upgrade that to level 2. After the first 15 seconds, he'll have 275 coins (500 + 75 from the past 15 seconds but spent 300 on the tower). He'll send 12 zombies for his wave (now at 155 coins).
Next 15 seconds (now at 00:30):
-Player A now has 260 coins. Player A sends a full wave of zombies (now at 140 coins). Player A will have 70 XP. Player A then decides to build another level 1 TNT tower (now at 40 coins).
-Player B now has 410 coins. Player B sends a full wave of zombies (now at 290 coins). Player B will have 120 XP. Player B then upgrades the mage one more time to level 3 (now at 140 coins).
Next 15 seconds (now at 00:45):
-Player A now has 295 coins. Player A sends a full wave of zombies (now at 175 coins). Player A will have 130 XP. Player A then decides to upgrade the level 1 TNT tower to level 2 (now at 75 coins).
-Player B now has 395 coins. Player B sends a full wave of zombies (now at 275 coins). Player B will have 180 XP. Player B decides not to upgrade the mage tower yet (a level 3 mage tower is enough to shut down zombies).
Notice that player B is leading player A in terms of XP and coins. The next 15 seconds will allow player B to have the 10 CPS (1st gold mine upgrade) but player A will need to wait 2 more cycles to get the 200 XP. Even if player A decides to send 4 zombies instead of 2 zombies 3 seconds later (so at 00:18 instead of at 00:15), he'll still have much fewer coins than player B and have the 10 CPS mine at least 3 seconds after player B gets his.