As long as you put the time and effort into training, it doesn’t actually matter whether you start off with a collar and lead or harness. In fact with very young pups, ideally you start off without a lead and train close walking in the first instance.
OP asked for advice about which collar to buy, not how to train LLW. For all we know, they could be getting some help from a gundog trainer, hence the slip-lead advice. Some posters have pointed out that if he already pulls like a train, any collar/slip lead could damage his neck. OP still needs to be able to walk him while they are working on his lead manners, hence people’s concern. Using a harness doesn’t preclude using a slip lead or flat collar once he’s able to walk on a loose lead. I recommended a type of harness I have seen help people whose dog is already a strong puller, while they are training lead manners. Personally I use both a flat collar and a harness interchangeably depending on the situation with my dogs.
The collar vs harness vs slip lead debate has been around for a very long time, different trainers have different opinions on it. The vast majority of positive puppy classes are happy with either a flat collar or well fitted Y harness, because the focus is on training focus/attention/position and if you put the effort in and get the training right, it makes no difference where the lead is connected.
I have a personal dislike of head-collars and do think they are often (not always) used as a shortcut to control in the place of appropriate training, others feel the same about harnesses and others about slip-leads. What matters is that people understand that no ‘tool’ is going to fix a pulling issue. It’s a training problem and can therefore only be fixed through training.
I don’t think calling people lazy or worse, is necessary. Sometimes training goes wrong. Not everybody is an experienced or competent trainer, things don’t always go according to plan and in those situations it’s ok to use a training tool (as long as it isn’t punitive in any way) to manage the issue while a remedial training programme is actioned.