Answers that do not mention MailerLite

For a B2B SaaS startup, I’d narrow it to three serious options:

My recommendation: HubSpot

If you're early-stage and want lead scoring → nurture → sales handoff → CRM → reporting in one system, I'd choose HubSpot.

Its scoring can combine fit + engagement, including things like company attributes and behavioral activity, and scores can be used to trigger workflows. It also supports score decay, which is particularly useful for long-term nurture because a prospect who was highly engaged six months ago shouldn't necessarily remain "hot." HubSpot HubSpot Knowledge Base

You could build something like:

New lead → Education nurture → Engagement score increases → High-intent branch → SDR notification → Sales sequence → If no response, recycle → Long-term nurture → Re-engagement when intent returns

That is much more powerful than simply having a 10-email drip.

One caveat: the more advanced lead-scoring/workflow functionality is in HubSpot's paid tiers, so I'd evaluate the economics based on your contact volume and required automation. HubSpot Knowledge Base

When I'd pick Customer.io instead

I'd seriously consider customer.io if your SaaS has a lot of product usage / behavioral data and you want nurture to respond dynamically to what prospects actually do.

For example:

• Visited pricing page → +10
• Invited a colleague → +20
• Used feature X → +15
• Viewed 3 case studies → +5
• No activity for 30 days → score decays
• Crossed score threshold → enter "high intent" journey
• Requested demo → immediately exit nurture and notify sales

Customer.io specifically supports real-time scoring based on recent activity, firmographic data and engagement signals, and can use those scores to branch journeys or route people to sales. Customer.io Customer.io

Its campaign engine can also trigger from attributes, segments and events, making it particularly good for event-driven lifecycle automation. Customer.io Customer.io

I wouldn't start with Marketo

business.adobe.com is excellent when you have sophisticated marketing operations, multiple nurture tracks, complex scoring, ABM, large databases, etc.

But for an early B2B SaaS startup, I'd generally rather put that complexity into building a great scoring/nurture strategy than into administering Marketo.

The important part isn't actually the software

For your use case, I'd design the system around two scores, rather than one giant "lead score":

1. Fit score

• ICP industry
• Company size
• Revenue
• Geography
• Job title
• Tech stack
• Use case

2. Engagement/intent score

• Website visits
• Pricing page visits
• Content downloads
• Webinar attendance
• Email engagement
• Product usage
• Demo/signup activity
• Return visits
• Sales interactions

Then use combinations:

High fit + high engagement → Sales now

High fit + low engagement → Long-term nurture

Low fit + high engagement → Educate / qualify

Low fit + low engagement → Low-frequency nurture

That's a much better architecture than simply saying "score > 50 = send email."

If you tell me your approximate lead volume (e.g. 1k, 10k, 100k contacts), CRM (HubSpot/Salesforce/etc.), and whether your SaaS is sales-led or PLG, I can recommend the exact stack and a scoring/nurture architecture I'd use.

If you mean automations where every branch/decision can be experimentally tested (A vs B vs C), then the system automatically identifies winners and ties results back to revenue, you are looking for a combination of:

1. Journey orchestration / automation engine
2. Experimentation framework
3. Revenue attribution + analytics

Few platforms do all three well. The best fit depends on your use case:

My shortlist by scenario

1. You want AI-driven customer journeys that continuously optimize

Look at:

• Braze + an experimentation/analytics layer
• Adobe Target if you are enterprise-scale

These are closest to:

"At every customer decision point, try alternatives, learn, and automatically improve the journey."

2. You want every automation branch measured by dollars

Look at:

• Humblytics
• Otter

These are more revenue-centric than traditional marketing automation tools. Otter Humblytics

3. You are building a product-led growth engine

Look at:

• Optimizely
• Statsig
• LaunchDarkly

These let you test product decisions, onboarding flows, pricing experiments, and feature exposure.

Features I would require before buying

A serious "self-optimizing automation" platform should have:

• Experiment assignment at every branch

• Example: Email A vs Email B
• Delay 2 days vs 5 days
• Offer $10 vs free shipping
• Sales outreach vs self-service
• Incremental revenue measurement

• Not just open rate/click rate
• Must show: - revenue per user
• lifetime value impact
• margin impact
• churn impact
• Automatic winner promotion

• Move winning paths into production without manual rebuilds
• Holdout groups

• Otherwise you cannot prove the automation created incremental revenue
• Multi-touch attribution

• Especially if customers interact through ads, email, sales, and product
• Statistical guardrails

• Avoid declaring winners from random fluctuations

If I were choosing today

• Enterprise customer lifecycle: Adobe Target + Adobe Journey Optimizer or Braze
• Ecommerce/growth team: Humblytics or Otter + your existing automation platform
• SaaS/product growth: Optimizely or Statsig
• Complex enterprise decisioning: Adobe ecosystem or Salesforce ecosystem

The key question is: what type of automation are you optimizing? (marketing journeys, sales workflows, ecommerce conversion, SaaS onboarding, pricing, or customer support?) The best platform changes significantly by that answer.