Calabrese and Dicicco are good "open pollinated" varieties.
Check out this evaluation that I read last spring. The url will not execute, so here is my whole archived article:
1985 BROCCOLI PROJECT RESULT SUMMARY
by Nancy Garrison, Horticultural Advisor, Santa Clara County
http://www.mastergardeners.org/picks/broccoli.html We grew 18 different varieties of broccoli at the Santa Clara Deciduous Fruit Field Station last year. Our primary objective was to compare the varieties with regard to taste, size of heads and shoots, and quality and length of side shoot harvest. Our second objective was to compare three different planting dates, using the Di Cicco variety.
Our three planting dates for the Di Cicco variety were July 23, August 15 and September 5. The two earlier plantings did significantly better than the September planting in all respects. They each produced 4 times more broccoli than did the September planting. The plants from the September planting were no more than a foot high and had an average head size of 2 1/4". The later plantings of Di Cicco grew 3 feet tall and produced great quantities of broccoli (mostly from side shoots) for 3 months.
We planted the following varieties:
Calabrese, Di Cicco, Goliath, Green Comet, Green Duke, Green Mountain, Italian Green Sprouting, Morses 4638, Packman, Paragon, Premium Crop, Purple Sprouting, Romanesco, Royal Cruiser, Spartan Early, Waltham 29, White Grenoble, White Sprouting
The qualities we were looking for in a variety were:
1. Average head size between 4" and 6"
2. Firm, tight, overall attractive heads
3. At least a 2 month harvest length from the time the first head is cut to the time the last high quality side sprout was cut
4. Acceptable flavor -- surprisingly, there were hardly any noticeable differences in this characteristic
5. Pleasing color of heads and side shoots
6. Good production of high quality (large, tight, somewhat uniform) side shoots for a 2 month time period. This was the characteristic which had the greatest variation between varieties.
The following is a brief description of the varieties we grew.
Di Cicco and Italian Green Sprouting -- These two varieties are very similar, but the latter had average head sizes of nearly 4" whereas Di Cicco averaged a little over 2 1/2". Both yielded about 2 lbs. total per plant over the 3 month period in which they were harvested. They produced small heads and large quantities of fair quality side sprouts over a very long period of time (3 months or longer).
Goliath -- As the name suggests, this variety produced very large heads, which were quite uniform in size and maturity. Average head size was nearly 6" in diameter and 3 lbs. in weight. It also produced very large, high quality side shoots for 2 1/2 months, which averaged 2 1/2" in diameter and yielded an average of 2 lbs. of side shoots per plant.
Green Comet -- This variety produced very uniform, medium large high quality heads, which averaged 3/4 lbs. and 5 1/2" in diameter on compact plants. The plant produced large, high quality sprouts for almost 2 months, after which time they continued to produce, but were of much poorer quality.
Green Duke -- Medium sized plants produced most of their heads within a 2 week period. Average head size was 5 1/2" in diameter and nearly 1 lb. in weight. There was a lot of variability in head size though, ranging from 4"-8" in diameter. It produced good quality, medium sized side shoots for 3 months. Each plant averaged a total weight of nearly 2 1/2 lbs., with 1 1/2 lbs. side shoots.
Green Mountain -- Performed very poorly--not worth describing.
Packman -- This variety was comparable to Goliath in all respects, except average head weight was just under 2 3/4 lbs. Average head size was a little over 5 3/4". It produced a hearty crop of large, high quality side shoots for 2 1/3 months.
Paragon -- Most of the heads of this variety matured in just one week (not a particularly good characteristic for a home garden variety). Average head size was almost 5" in diameter, but variable, ranging from 3 1/4"-7". Plants were medium sized and produced a pretty good crop of large side shoots.
Premium Crop -- Tall, upright plants produced variable sized heads, with the majority maturing within a week of each other. They ranged in size from 3 1/2"-7', averaging 5" and 3/4 lbs. The heads grew very low in the center of the plant (recessed). We harvested an average of 13 side shoots per plant over a 2 month period, which averaged 3/4 lb. per plant for a total of 1 1/2 lbs. of broccoli per plant.
Purple Sprouting -- We liked what we had growing under this, but there was negligible purple coloration, which makes me wonder whether the variety was actually Purple Sprouting.
Romanesco -- The first heads were produced nearly 2 months after most of the other varieties bore. They were unique in color and form, being a beautiful, moss lime green color with a sculpted form. There was extreme variability in head size, ranging from 5"-11 1/2", averaging 8 1/2" and 3 1/4 lbs. Some heads were beautiful and some were almost grotesque. This variety does not develop any side shoots, but develops one very dense head, similar to a cauliflower.
Spartan Early -- This variety didn't perform well for us. It was off colored and of poor texture and form. The heads were variable in size, ranging from 2"-6" in diameter, averaging 3 1/2 lb. and almost 1/3 lb. The plant was very short and compact.
White Sprouting, White Grenoble and Royal Cruiser -- These 3 varieties performed similarly, in that all of them produced very small, negligible heads 2 months after the others. The heads were more like side sprouts rather than heads.