Finals day takes place at Edgbaston on Saturday 15th. The semi final draw was as follows

Lancashire v Worcestershire
Sussex v Somerset

Outright odds tell us what a close contest this is expected to be. Bet365 are typical in being 11/4 each of four! Each semi-final is 10/11 each of two Looking at each team in turn:
Lancashire finished 3rd in the North Group with an 8-5 record then won a low scoring quarter-final at Kent.

The talented wicket-keeper batsman Alex Davies has scored 525 runs at the top of the order in the competition so far and Liam Livingstone is now back from injury, one of the best ball strikers in the county game. Jos Buttler will be back too and this is a talented batting line up

The leg-spin of Matt Parkinson has led the way on the bowling front with 23 wickets

Worcestershire have been one of the coming one day sides for a couple of seasons, and finished 1st in the North Group with a 9-4 record then beat Gloucestershire comfortably in a home quarter-final

Their young talent mainly comes in the batting line up where Ferguson and Clarke are followed in the middle order by the huge hitter Ross Whitely. In the bowling ranks the unheralded Pat Brown, a 20 year old medium pacer, has emerged with 27 wickets
Sussex finished 3rd in the South Group winning 7 of their 10 completed games but suffering weather variance with 4 rained off no results denying them a home quarter final. They travelled to Durham for their quarter final and were convincing winners
Their main strength is in the bowling ranks where Rashid Khan and Jofra Archer have combined for 35 wickets in 22 appearances.

Rashid was recalled by Afghanistan after the group stages and also misses now finals day which is a huge loss.
Somerset finished 1st in the South Group with a 10-4 record and smashed 230 at home to beat Notts in their quarter final.
New Zealander Corey Anderson has hit 466 runs from the middle order (Taunton is a very hittable small ground, which helps) and the bowling line up is full of England fringe talent such as the Overtons and Gregory

Looking at the finals day afresh if I were to make a choice I would suggest Lancashire as the likely winners.
My suggested bet is in the Sussex v Somerset semi-final where Sussex number three Laurie Evans is 7/2 with Betfair/Paddy Power to be top Sussex run scorer

Evans has 554 runs in 12 innings in the competition this season, over 200 runs clear of the former England international Luke Wright with 327 (ten innings). He should be clear favourite and isn’t and is one of the best bets for finals day