I can so vouch for the gel seat. Hubby and I bought bicycles a couple summers ago. I wasn't at my highest weight, but I was at least 20 lbs heavier than I am now.
I tried to do online research, but I couldn't find any information on the weight limits of bicycles, so I wasn't even sure a bicycle was a possibility at my size. Finally, I had to break down and ask a live person. Hubby and I went to a bike shop, where instead of laughing at us (which I was expecting) the young, skinny, competitive cyclers that owned the shop gave us enthusiastic pointers. They told us to go for simple, sturdy construction (with no springs and fancy suspension systems).
We decided on Walmart cheapies to gain practice on, with plans to buy good bikes when finances warranted.
My hubby (fat, but Mr. No Butt) was fine on the standard seat. I however was in excrutiating pain (both in the butt and more frontal inner thigh region - I think I walked bow-legged for a few days, and didn't let hubby near me, if you know what I mean - he teased me that I had been sexually assaulted by the bicycle, and I sort of felt that way).
The biggest gel seat Walmart sold solved my problem. Hubby can't ride anymore because of balance issues with this nerve and joint problems, but I plan on upping my tolerance this summer and fall. If I can get to the point that I'm on the bike more than an hour, I'm going to start looking online for an even wider gel seat.