I personally prefer Aqualung Titan regs, but again, user preference. I think it must weigh (unofficially) half of what any other regulator I've tried does thus far, feels incredibly comfortable to use as well. You can try a website like leisurepro or scuba.com, go to their regulator sections and select highest customer reviews. Read the positives/ negatives to each one. Picking a regulator is such a personal matter that it comes down to comfort once you know what features you want. It's like shopping like a digital camera these days, if they all don't have the same basic function, no one buys it. Atomic regulators always rank high in quality, they were something that I was looking at as well.
The venturi knobs (for adjustable ease of breathing) may make a difference depending on the climate you're diving in. If you don't have a cold water reg but you're diving in cooler waters, turning the knob down so that you have to draw a stronger breath may protect against annoying freeflows from the second stage if it's not a "huge" temperature issue. If it's too cold however, no amount of diver adjustables will improve this, only cold water solutions. The knob on mine does make a difference, but it's not "huge". With other regs without these you need your LDS to change this for you if you don't have the tools yourself at home. Can be annoying in a pinch. Again, like swivels, it's just another gimmick really but something I personally like.
I find it clever that the dive shop you're doing your training with only has swivels for rental, I don't want to sound like a conspiracy theorist, but clever if that is indeed to get people spending more. If not and it's genuinely about comfort, well- kudos for the thought of the customer; may not be entirely beneficial though because at least when you first try scuba/ learn you understand that it is an incredibly different feeling having all the gear on, the less entertaining bells and whistles to know what the minimum gear you need, the easier to learn what a standard rig looks like imo. Oh well, torn!