Combine the two and powerslay! It means that you'll be using the most effective att/str boost prayers and super pots to OSRS Gold For Sale complete your assignments, and you can also use a cannon is also an option if to/can afford to. This could get you upwards of 100k exp/hr at higher levels, which is as much or more than armoured zombies and bandits. It also means you don't risk looking ridiculous as a 138 with a 70 slayer.
Gear must include: Barrows gloves, from RFD. Dragon boots. Full slayer helm, black mask until you get it. Wear armour that you can proselytize if you're using prayers, and barrows if don't. Whip, try to obtain an uncontrollable rapier as fast as you are able to. Dragon Defender, antidragon shield to tackle dragon tasks (DFS is overkill, don't spend the time on one).
Amulet of glory, try to obtain the fury whenever you are able. Ardougne cape 3, or soulwars cape. While that does sound interesting but wouldn't it defeat the purpose of slaying? The fun of training Slayer is something new to finish every job, and that's sure good. But isn't it also to earn money? I'm pretty sure that someday prayers would increase prices to the point where I'm losing money, isn't it?
By the way, thanks to everyone who has offered advice. Even with prayer potion, you are most likely to make money from slayer, they are very affordable. By the drop alone you could make some money, but If you don't, then you can purchase Slayer Dart Runes from the master of slayers for 35 Slayer points (you receive 36 for performing 2 tasks from Kuradel) is about ~70k which is decent and could yield quite a bit of cash if put your money into this instead of cancelling or blocking activities.
Is it possible to train on bandits but not yet? Or should I take a look at Giant spiders inside the Stronghold till 70 def, then shift to RS 2007 Accounts bandits? Sumona requires 85 combat and Smoking Kills which you should do when you're a slayer.
