Okey-dokey. Here goes: If you think the Kohler Portrait works fine, you are going to be BLOWN AWAY by the Toto.
We had that exact Kohler toilet, which we got so it would "match" the beautiful Portrait sink we installed. (By the way, that's the number 1 reason people bought that toilet, because both it and the sink are very attractive.) The Ingenium flush sucked. It literally would clog the moment you put any kind of solid material in it. It required repeated flushing to keep low the amount of material going into it, and even then it still clogged. Ir required plunging on at least 80% of the visits to the restroom. I finally hit it with a sledgehammer and replaced it with an original Drake. It was one of the happiest days of the last few years for me. Nobody, but nobody, notices that the original Drake doesn't "match" the sink. To show you that much of the time only the homeowner notices the style of the toilet, some people commented that we had "fixed" the toilet without realizing that we had replaced it with one that didn't look anything like what was there. What people do notice is that it works flawlessly.
That toilet was so bad that I really thought I should start a class-action suit against Kohler for foisting such a defective product on the masses. It was so bad that I will always personally purchase another brand over Kohler if there is any reasonable alternative to the Kohler product (but I will always give Kohler a fair shake in my evaluation for myself as to whether their product is better; if it is, it bears considering, but if it's equivalent, I'm buying the other guy's product). That they still sell this Ingenium Flush is shameful.
I really thought that when I removed the toilet I would find some clog in the outlet or in the drain, but nope. I bolted the new Toto in and it's been Nirvana ever since.
Sounds like we have similar homes, because I had the exact same issue in another bathroom where the toilet I was replacing was perpendicular to the clawfoot tub. I was installing another original Drake, and I got the Round to replace a Round 1950s toilet because I thought that the extra length of the elongated bowl might make it uncomfortable either to walk past or to sit on. The round is fine (and flushes great!!!), but once I had it in, and used both it and the elongated original Drake I installed in place of the Portrait, I realized that the elongated would have been fine. You sit in the same position on the elongated, it just gives you a little more toilet in front of where you sit. So your body, legs, etc aren't any closer to the tub than they would be on the round. So as long as you can easily fit past it, which in my case one easily could in retrospect, it's worth getting the elongated for a little extra comfort, particularly for the guys.
So, like I said, the round is fine, but sitting on the elongated is a better experience for most people. If you "hate round bowls" then don't sweat it and get the elongated. The elongated Promenade is 28.25 long, plus .75 between the tank and wall, so it's going to be 29" from the finished wall, which gives you an extra inch over your Portrait. That's a good compromise.
If you're in the mood to splurge (like an extra $300 or so street price [not inflated list price]), you might look at the Toto Guinevere, as it has a little Portrait-ish look to it. It's a one-piece, skirted toilet, comes standard with Sanagloss, the Double-Cyclone Flush, Comfort Height and 1.28gpf flush. It's one of Toto's nicest gravity toilets, and it may not be worth the extra bucks if you like the Promenade, but I just thought I would mention it. Here's the spec sheet: http://www.totousa.com/Portals/0/Pro...74224CEF_G.pdf It does come with a seat included, so you can deduct say $45 when calculating the difference in price. Still, it's a lot more and the Promenade is a great toilet.