Wow, I don't know that I would enjoy riding with someone less than supportive - takes the fun out of it for me.

There are many factors and these seem to come to light when going up hill.

Rider - some people are better at flats, some at hills, some at downhills. Much depends on what you enjoy, your physical characteristics. Back when, I was okay on flats and such, not necessarily fast relative to the regular friends I rode with. But once we started going uphill, I was in the upper group - I trained for hills and, I guess, my muscle group and weight were more suited to that.

Bike - Given your current state, you would see a difference with a lighter bike. Would it be enough to stay up with the group - can't really say. Many factors on a bike - state of tune (chain, bearings); gearing (are you running out of gears, are you spinning or mashing up hills); tires (I've seen night and day difference just in tires); do you like the bike (the more you like/love your bike, the faster one seems to go - at least for me).

Compare against yourself not others. We are all different, different styles, different strengths. I stopped comparing to others because of that. No matter how much I trained, I could not pull at the speeds some of my friends could, but I did track my own progress and I could see I had improved, say, from point A to point B in time.

On the heavy bike note - My road bike is a 20 pounder and is a race frame. Very fun to ride. My commuter is probably a 30 pounder AND is also fun to ride. I have had guys on light road frames blast by me on the start of my final climb home (about 100' in half mile) only to start slogging about half way up and I go by in my normal, steady RPM at my pace. They either failed to shift or just did not anticipate the effect of the variable pitch of the road and went at it too hard, too soon. I've also been totally left in the dust.

Good luck in your training and improvements - you will get stronger and faster. Find some supportive friends/groups to ride with, that makes so much difference.