Trailer wiring, 4 flat, 4 round, 7 round?

So I have what appears to be either a factory or dealer installed towing package on my 03 tacoma. There's a little box under the drivers side rear seat storage cubby that has "toyota denso" all over it and has a sticker that says "converter with bracket".

So I have a flat 4 pin wiring harness and I recently discovered that it's corroded to hell. I'm going to replace it and was wondering if I should just replace it with another flat 4, or upgrade to a round 4, or maybe something else? I'm leaning towards doing a 4 round and carrying a flat adapter, purely because the 4 round design looks more robust and weatherproof.

The only thing I see myself ever towing in the future are things like maybe a small camping trailer, or a small boat, or car/utility trailer.

 

I'd stick with either a flat 4 or a 7-pin round. If you don't tow anything with brakes or plan on towing anything with brakes, the flat 4 is all you need. There are flat 4 plug and play kits that install in less than 30 minutes, no wire splicing required. Use dielectric grease on the flat 4 this time and the pins won't corrode.

I'd avoid the round 4 because, frankly, I've never seen a trailer with that kind of connection. I'd stick with the more common flat 4 or 7-pin.

 

If you keep the 7 pin just buy the 7 to 4 pin adapter that way it will fit most any thing. The "converter" is for the single brake/parking bulb system found on most trailers.

 

If you are going to tow anything with brakes, upgrade to a 7 round plug. You will need to add a brake control but those are pretty easy to wire.

4 flat is good if you arent towing anything with brakes.

4 round is outdated and not used anymore.

 

Go with the 7 pin. You can always use a $6 converter to go from 7 to 4 but you can't go the other way around.